REDUCE COMPUTER ATTACKS

Description

[0001] The invention relates to the field of telecommunications, and in particular concerns the implementation of reliable and robust mechanisms for protecting resources (network, terminals connected to a network, servers connected to a network), to respond to computer attacks such as, for example, "denial of service" (or "DDoS", for "Distributed Denial of Service").

[0002] A DDoS attack is an attempt to make resources (e.g., network or computing resources) unavailable to their users. In most cases, such attacks can be deployed on a massive scale by compromising several hundred thousand endpoints and using these infected hosts to amplify their damaging power.

[0003] When so many machines are involved in the execution of attacks, the implementation of appropriate filtering policies, i.e., policies capable of isolating traffic from all infected machines, is all the more complicated since these machines can be massively distributed across several separate networks. Furthermore, the duration of such attacks (one hour or more) as well as their propagation further complicate the task of so-called "DPS" services (for "DDoS Protection Services") that may be mobilized to resolve these attacks.

[0004] More and more DPS offerings are hosted in the cloud, not just within the infrastructure operated by access providers. These deployments raise issues such as early detection of attacks, as the DPS service is not necessarily present on the data routing paths to reach a network that is the victim of an attack.

[0005] Workarounds can be considered such as establishing "tunnels" to force all traffic from a site or network to be inspected by the DPS service. However, this implementation based on the establishment of tunnels considerably increases the latency observed by users and imposes sizing constraints on the DPS service to be able to process all traffic without degrading performance or the level of experience as perceived by the customer. In addition, such tunnels are preferred attack vectors.

[0006] Even if the DPS service is present on the path of traffic entering a network (case of access providers offering the DPS service), additional complications are encountered in identifying suspicious traffic. Indeed, with the increase in encrypted traffic, notably transported over UDP (User Datagram Protocol), it is difficult to distinguish legitimate traffic (i.e., that received with the consent of a user) from suspicious traffic. The difficulty of accessing in clear text control messages similar to those of TCP (for "Transmission Control Protocol" - typically the exchange of messages of the type SYN / SYN-ACK / ACK) significantly complicates the verification of the consent of a machine to receive traffic.

[0007] A client / server architecture specified by the Internet Engineering Task Force (IETF) aims to provide a mechanism for reporting the detection of suspicious traffic, or even a confirmed attack, so that appropriate mitigation measures can be implemented as quickly as possible. This architecture is called "DOTS" (for "DDoS Open Threat Signaling"). It is designed to allow a DOTS client to inform a DOTS server that it has detected suspicious traffic potentially characteristic of an ongoing DDoS attack, and that appropriate mitigation actions are required. "Mitigation" action is understood to mean any type of action intended to reduce or even eliminate the impact of the detected or suspected attack (e.g., dynamic implementation of a traffic sink, etc.).

[0008] The example of the figure 1 shows the case of an ATT attack suffered by a DC client domain. Upon detection of the attack on a CiB target, the DOTS client (CL DOTS) of the domain sends a message to the SER DOTS server to request assistance for mitigation of the detected attack (MITIG). The latter coordinates actions so that the traffic associated with the denial of service attack is no longer routed to this domain, as illustrated in figure 2 . Thus, only “consented” traffic is routed.

[0009] In reference to the figure 3 , the DOTS solution uses two communication channels: a Signal Channel, used only while DDoS attacks are ongoing. A DOTS client can use this channel to request help from the DOTS server by informing it that an attack is in progress; and a Data Channel, used if and only if no DDoS attack is in progress. For example, a DOTS client can use the Data Channel to install filtering rules, such as filtering traffic received from certain addresses or that intended for a given machine.

[0010] DOTS is an architecture designed to facilitate the handling of attack mitigation requests issued by a client and received by a server typically operated by the DPS service provider. However, depending on different contexts (nature of the attack, location of the source at the origin of the attack, amplitude, perimeter and scope of the attack, in particular), the DOTS mechanism may prove insufficient or even ineffective. US2018 / 007518A1 discloses the use of a fleet of drones to provide a mesh network of assistance for initial calls or communications from a disaster area.

[0011] The present invention improves the situation.

[0012] To this end, it proposes a method for managing assistance to a communications network capable of carrying traffic characteristic of a computer attack, the method comprising: upon detection of a computer attack, identify at least one first node of the network, requiring mitigation intervention, and identify a traffic routing policy in the network, control a movement of at least one mobile object, and comprising at least one communication interface, to connect the mobile object to at least one second node of the network determined relative to the first node according to said traffic routing policy, control at least part of the traffic routed by the network to redirect said part of traffic to the mobile object via at least said second node of said network.

[0013] For the purposes of the invention, a node requiring mitigation intervention is a node typically identified in a mitigation plan as being the target, source or collateral victim of an attack, or a node involved in the implementation of this mitigation plan (for example, by executing a traffic redirection policy, by modifying its routing table). The term "mitigation plan" means all the actions and measures implemented for the mitigation of an attack.

[0014] Thus, the invention proposes a treatment of attacks based on a principle of mobility. This ability to be mobile makes the implementation of the invention particularly efficient in the processing time of mitigation requests and in the execution of mitigation actions.

[0015] In one embodiment, the aforementioned second node corresponds to the first node. This is a mode detailed below with particular reference to the figure 12 , and called “local loop”.

[0016] Alternatively, the second node is distinct from the first node, which may correspond to a “parallel” or “bypass” mode detailed further below with reference to the figure 14 .

[0017] In one embodiment, a plurality of mobile objects are provided, each comprising at least one communication interface for communicating at least between mobile objects, and a first mobile object, among said plurality of mobile objects, is controlled to connect at least to said second node of the network.

[0018] These mobile objects can be, for example, drones constituting a fleet of drones as presented in the examples of implementation below.

[0019] The identification of the first node of the network and the traffic routing policy in the network can be carried out by a mitigation server linked to at least one of the mobile objects (including the case where the mitigation server is embedded in one of the mobile objects).

[0020] The computer attack can be detected by a second mobile object, connected to the network, which may (or may not) be the same mobile object as the aforementioned first mobile object, connected to the second node of the network.

[0021] Alternatively, the computer attack can be detected by a third node in the network.

[0022] Detection can be performed by a node that does not require intervention and / or is not involved in the mitigation plan either.

[0023] Alternatively, this third node may correspond to the first node mentioned above.

[0024] Generally speaking, the aforementioned traffic, characteristic of a computer attack, can be sent from at least one node in the network (or not). This traffic, characteristic of a computer attack, can also be sent to at least one node in the network. In addition, it can be local, in at least one node in the network (typically the case of viruses).

[0025] In one embodiment, the mobile object may be equipped with processing circuitry comprising computing resources providing computing capabilities to process at least said portion of traffic redirected to the mobile object.

[0026] The required intervention may be traffic mitigation in response to a denial of service attack, for example (DDoS).

[0027] In one embodiment, the mobile object is configured to analyze and filter at least said portion of traffic redirected to the mobile object (notion of traffic cleaning or “scrubbing” in English).

[0028] The mobile object may be configured to establish communication by radio frequency link to connect to at least said second node, the movement of the mobile object being remotely controllable to approach a geographical position of the second node.

[0029] Such an achievement in particular makes it possible to promote the emergence of protective networks, capable of detecting and anticipating attacks even before they reach their targets.

[0030] Such an implementation advantageously allows: to activate on demand a suspicious traffic filtering function in order to “clean” the network of any trace of this traffic (“scrubbing”) as close as possible to the source (target) of the attack; to reduce the load on the equipment involved in the propagation of the attack traffic, so that legitimate traffic can continue to be routed in the best conditions despite the presence of the attack traffic and independently of its volume; to dynamically and automatically implement protection measures for any location of the resources mobilized in the mitigation of the attack while preserving the continuity and quality of the services subscribed to by users; to offer a “portable” and mobile DPS service for more effective mitigation; to exploit the resources of a mobile, portable DPS service, capable of detecting and intervening at any time and at any location (in the network) where an attack has been detected;to ensure the continuity of services offered by the protected network.;

[0031] In an exemplary embodiment, the method may comprise: a transmission of a graft message to the mobile object, to control a movement of the mobile object and establish a connection of the mobile object to the second node, designated in the graft message, a transmission of a routing policy message to the mobile object, to control at least one traffic routing rule by the mobile object, a transmission of a (second) routing policy message to at least the second node this time, to control at least one traffic routing rule by the second node.

[0032] The method may further comprise: upon receipt of a request to end assistance for processing the computer attack, control the object to analyze at least said part of the traffic, and, depending on the analysis: * confirm an end of assistance, or * decide on a time delay before the end of assistance.

[0033] In the event of confirmation of the end of assistance, it is possible to provide for the transmission of a cessation of intervention message to the mobile object.

[0034] Routing rules can also be provided that include an instruction for the gradual resumption of normal traffic by the first node requiring intervention, before the end of assistance.

[0035] The transmission of these various messages can be carried out by at least one mitigation server linked to the mobile object.

[0036] The present invention also relates to a computer program comprising instructions for implementing the above method, when said instructions are executed by a processor of a processing circuit.

[0037] This processing circuit can typically be implemented in a mitigation server of the type presented above. The processing circuit can typically comprise a communication interface with, for example, at least one node of the network and at least one mobile object, as well as a memory storing instructions of the computer program, and a processor for executing them. This computer program can implement a general algorithm such as that illustrated in the figure 25 as an example.

[0038] The present invention also relates to a system for managing assistance to a communication network capable of routing traffic characteristic of a computer attack, comprising at least: an object, mobile, and comprising at least one communication interface, to connect to at least one node of the network, a mitigation server configured to, in response to a detection of a computer attack: * identify at least one first node of the network, requiring mitigation intervention, * identify a traffic routing policy in the network, * control a movement of the mobile object to connect the mobile object to at least one second node of the network, determined relative to the first node according to said traffic routing policy, * control at least part of the traffic routed by the network to redirect said part of traffic to the mobile object via at least said second node of said network.

[0039] The present invention also relates to a mitigation server for assistance to a communications network likely to route traffic characteristic of a computer attack. In particular, the mitigation server being configured to, in response to a detection of a computer attack: * identify at least one first node of the network, requiring mitigation intervention, * identify a traffic routing policy in the network, * control a movement of at least one mobile object comprising at least one communication interface, to connect said mobile object to at least one second node of the network, determined relative to the first node according to said traffic routing policy, * control at least part of the traffic routed by the network to redirect said part of traffic to the mobile object via at least said second node of said network.

[0040] The implementation of the invention then makes it possible to block (or at least limit) attacks which can be multifaceted (typically denial of service, propagation of computer viruses, identity theft for the purpose of data theft, "ransomware", etc.) on targets or relays used to propagate the attack traffic which can be extremely varied (fixed and mobile terminals, connected objects, Web servers, network resources, IP prefixes, etc.). As such, the implementation of the present invention makes it possible, via the various embodiments proposed, to resolve the following technical problems which are usually likely to penalize the effectiveness of a conventional DOTS-type architecture.

[0041] The security policies implemented by operators are essentially based on traffic filters activated at various fixed and static locations in the network (routers, firewalls, access switches to cloud infrastructures, access and traffic collection equipment, etc.) and the complexity of their dynamic adjustment depending on an ongoing attack is proportional to the scale of the attack and the intervention capabilities of the operator. On the contrary, the invention offers “modular” and “adjustable” protection depending on the attack.

[0042] Access to resources involved in implementing security policies may be compromised when an attack is underway and when it affects all or part of these resources. It is particularly difficult or even impossible to access these resources, modify a configuration or install patches while an attack is underway. The invention provides a solution to this problem by allowing capacity expansion of network resources and traffic redirection.

[0043] Furthermore, in the state of the art, the attack traffic is propagated in the network at the risk of degrading the level of quality associated with the services subscribed to by the users; the routing efficiency of legitimate traffic is thus degraded by the propagation of the attack traffic. This approach can impact the quality of experience associated with this network. On the contrary, the invention preserves the quality of experience offered by the network by proposing a redirection of the traffic and by allowing a mitigation intervention as close as possible to the target of the attack and / or the source thanks to the mobility of the objects involved in the mitigation.

[0044] Furthermore, in conventional techniques, the processing of requests for implementing mitigation actions may be far from the location where the attack was detected, at the risk of penalizing the time from which the mitigation actions will be effective. The DPS service must ideally be able to be requested and act as close as possible to the location where the attack was detected, which is made possible by the invention thanks to the mobility of the objects which can thus intervene as close as possible to the target and / or the source of the attack.

[0045] Finally, the invention does not require the use of tunnels to reach a DPS service, which as mentioned previously, is not optimal, tunnels being preferred attack vectors.

[0046] Other characteristics, details and advantages of the invention will appear on reading the detailed description below, and on analyzing the attached drawings, in which: Fig. 1 [ Fig. 1 ] illustrates an example of an attack (before a DOTS solicitation), Fig. 2 [ Fig. 2 ] illustrates an example of an attack (after DOTS solicitation), Fig. 3 [ Fig. 3 ] schematically illustrates DOTS (signaling and data) channels, Fig. 4 [ Fig. 4 ] illustrates an example of a network protected by several fleets of mobile objects (here drones), Fig. 5 [ Fig. 5 ] illustrates an example of a network protected here by several fleets, Fig. 6 [ Fig. 6 ] illustrates different cases (A to D) of examples of possible configurations for the implementation of the above method, Fig. 7 [ Fig. 7 ] illustrates an example of activation of mitigation actions triggered following a request issued by an agent located in the network, Fig. 8 [ Fig. 8 ] illustrates an example of mitigation activation triggered from a mobile fleet, Fig. 9 [ Fig. 9 ] illustrates an example of activating mitigation triggered from a mobile fleet in a case where the mitigation server is not part of the monitoring fleet, Fig. 10 [ Fig. 10 ] illustrates an example of mitigation activation triggered from a mobile fleet requested by the surveillance fleet, Fig. 11 [ Fig. 11 ] illustrates an example of launching mitigation actions from a “static” mitigation server (non-mobile, not embedded in a fleet of drones), Fig. 12 [ Fig. 12 ] illustrates an embodiment of a local capacity extension by use of a drone, Fig. 13 [ Fig. 13 ] illustrates an alternative embodiment of a local extension relative to the figure 12 , Fig. 14 [ Fig. 14 ] illustrates an embodiment of a capacity extension in “parallel” or “bypass”, an alternative to the mode illustrated in the figures 12 et 13 , Fig. 15 [ Fig. 15 ] illustrates an example of mitigation with the intervention of a single drone, Fig. 16 [ Fig. 16 ] illustrates an example of filtering suspicious traffic within the NW network by mobile scrubbing, Fig. 17 [ Fig. 17 ] illustrates another example of traffic redirection within the NW network by mobile scrubbing, Fig. 18 [ Fig. 18 ] illustrates an example of multi-fleet cooperation in routing traffic during a security incident, Fig. 19 [ Fig. 19 ] illustrates an example of interception of unwanted “offload” traffic, Fig. 20 [ Fig. 20 ] illustrates an example of an intervention to route outgoing traffic from the NW network, Fig. 21 [ Fig. 21 ] illustrates an example of an intervention to route incoming traffic to the NW network, Fig. 22 [ Fig. 22 ] illustrates an example of message exchange for implementing mobile mitigation operations, Fig. 23 [ Fig. 23 ] illustrates an alternative example of message exchange for implementing mobile mitigation operations, Fig. 24 [ Fig. 24 ] illustrates yet another example of message exchange here via a fleet controller, and Fig. 25 [ Fig. 25 ] summarizes the main steps of an example of a method within the meaning of the invention.

[0047] The method described below applies to any type of mobile object (drone, autonomous car, stratospheric balloon, aircraft carrying one or more routers, etc.), even if it is subsequently used and represented in the figures of the drones for illustrative purposes. Thus, hereinafter, the term "drone" means an uninhabited aircraft ("Unmanned aerial vehicle" (UAV)), or an uninhabited ground vehicle ("Unmanned ground vehicle" (UGV)), etc., in a general manner and without any particular assumption as to the movement and autonomy capabilities of this drone.

[0048] The following attack examples relate to denial of service attacks, but the solution described applies to other types of attacks, such as the spread of computer viruses, exploitation of operating system vulnerabilities, etc.

[0049] The proposed solution is recursive: a fleet of mobile objects can be used for the purpose of mitigating a network composed of other mobile objects (for example, a network composed of aircraft, a vehicular network (Vanet, "Vehicular Ad-Hoc Network"), a MANET (Mobile Ad-hoc Networks)).

[0050] The solution does not describe how a mobile fleet can restructure itself (by excluding a drone from the topology for example, or by activating new connections, mutation / evolution of topology, etc.) to protect itself from an attack suffered by the fleet itself.

[0051] Furthermore, the functional structuring of a DPS service as well as its interaction with the resource(s) to be protected are known to those skilled in the art and the description below does not detail these particular aspects.

[0052] The communication sessions between the different elements described below are established for example using the DTLS (Datagram Transport Layer Security) protocol, in particular but not exclusively its version 1.3, or the TLS (Transport Layer Security) protocol, for example its version 1.2 or 1.3. The details of the (D)TLS exchanges and those concerning the management of security keys are not reproduced below.

[0053] Furthermore, it is assumed here that the various elements considered within the scope of the invention and intended to interact (e.g. mobile objects, mitigation server, network elements (also called nodes), agents, etc.) must mutually authenticate each other. Thus, messages received from a source usurping the identity of a legitimate element may be rejected by another element. In the same way, requests from network nodes not authorized to access the mobile DPS service described below are ignored. It is assumed in the following that this mutual authentication procedure is implemented by the various elements considered (mobile object, mitigation server, network nodes, agent, etc.).

[0054] Generally, one or more fleets of mobile objects are deployed for monitoring and mitigating attacks on networks or terminals / servers connected to these networks. Thus, separate fleets of mobile objects can be considered for network monitoring on the one hand and for mitigation operations on the other. Alternatively, one (or more) same fleet of mobile objects can provide monitoring and mitigation functions.

[0055] Furthermore, the following is generally considered.

[0056] Mitigation actions may involve border elements of a network (for example, "ASBR" routers, for "Autonomous System Border Router") or transit elements within this network. Furthermore, the implementation of the invention may make it possible to deal with the case of sources at the origin of an attack that may be hosted within the network infrastructure to be protected (typical case of "Man-in-the-Middle" (MITM) attacks, for example). Mitigation actions may relate to traffic (incoming, outgoing, or both - with, for example, dynamic creation of a traffic sink intended to eliminate attack traffic), and involve one or more nodes.

[0057] No specific assumptions are made about the underlying network topology or the type of traffic it carries. A network can be an operator network, but it can also be a network such as that used by IP connectivity or content delivery network (CDN), a network of autonomous cars, a sensor network, a connectivity network made up of airplanes, etc.

[0058] According to the invention and as mentioned previously, the same network can be protected by one or more fleets of mobile objects. With reference to the example of the figure 4 , three fleets of drones protect the same NW network. These three fleets F1, F2, F3 have distinct ranges (and thus different intervention perimeters). Fleets protecting the same network can also have the same intervention perimeter.

[0059] Furthermore, a single fleet can protect one or more underlying networks. Referring to the example of the figure 5 , a single fleet of F drones can protect two networks (NW1 and NW2). All or some of the drones making up the F fleet can simultaneously participate in mitigation operations on segments of these two networks. In this case, network identifiers, called “network_id”, are used to identify a network in an unambiguous manner.

[0060] The “network_id” identifier can be: a PLMN (“Public Land Mobile Network”) network identifier, an autonomous system number or “AS” (for “Autonomous System”), etc.

[0061] Each fleet is composed of one or more mobile objects. Each object is identified by a unique identifier called "object_id". This identifier can be an alias, a domain name, an IP address, a URI (Uniform Resource Identifier), an E.164 number such as MSISDN (Mobile Station ISDN Number), or other. Referring to the example of the figure 4 , the first fleet F1 (respectively, second F2 and third F3) is composed of 5 objects (respectively, 3 and 1).

[0062] Fleet size, sizing (i.e., the traffic capacity that can be carried / routed / processed by a fleet), services offered, geographic reach, etc. are specific to each fleet.

[0063] A single fleet can be composed of mobile objects of different types. For example, a fleet can be composed of UAVs, UGVs (defined above), and / or autonomous cars. These different objects coordinate to execute the required mitigation tasks.

[0064] A fleet can have at least one "mitigation server" service function or interface with one or more external mitigation servers. These mitigation servers can also be fixed servers or belong to another mobile fleet.

[0065] The "mitigation server" function can be provided by a single software instance or be composed of several elementary service functions, using Service Function Chaining (SFC) techniques. These service functions can be embedded in separate physical nodes.

[0066] Several fleets may have an identical configuration (size, sizing, services, etc.). However, a fleet can be dynamically modified to include new objects or support new services. For example, performing a new mitigation function may require the introduction of an additional drone, increasing the processing and routing capacity of the fleet, connecting to other networks, etc. These decisions may be made, for example, by an (external) controller responsible for managing the fleet, or by one or more “controller” functions on board some of the drones in the fleet.

[0067] A fleet of mobile objects can be connected to one or more other networks different from the network it protects, for example to optimize traffic flow (e.g. 5G, 4G, WLAN network, etc.).

[0068] Communication between two mobile objects of the same fleet can be direct (i.e. via associations without an intermediate network) or indirect (e.g. via a wide area network such as a 4G or 5G network). The selection of the communication mode is made according to the context of the communication (e.g. direct communication is used for the flow of attack traffic, while indirect communication can be used to instruct a mobile object to position itself in an intervention zone). Both communication modes can be maintained simultaneously.

[0069] Generally, several fleets can interconnect for coordination and efficiency purposes in the execution of monitoring and / or mitigation actions.

[0070] Referring now to the figure 25 , a general method within the meaning of the invention can begin for example with a step of detecting and triggering S-AM mitigation operations (for “ACTIVATION_MITIGATION”).

[0071] This involves activating (or triggering) mitigation operations via at least one fleet. Here, a mitigation server decides on the actions to be taken so that a fleet of mobile objects called "mitigation" connects to the network where an attack has been detected (as presented later in reference to step S-RR for "NETWORK_ATTACHMENT"), but also on the mitigation actions to be executed (step S-AM). Mitigation actions include in particular the identification of a traffic routing policy in the network which makes it possible to identify in particular the node(s) of the network to which the fleet must connect.

[0072] The connection and mitigation phases are not necessarily subject to a specific chronology: mitigation actions can be defined and prepared (for example, construction of new traffic filters, updating of the database maintained by the mitigation server and description of the attacks being processed in particular, etc.) without the intervention fleet being connected beforehand to the network where an attack was detected.

[0073] It is assumed here that dedicated ACT-AD security agents are activated within the network. One or more security agents may indeed be active in the network. The selection of network nodes embedding these active agents is a local decision for the network operator. Typically, these ACT-AD agents are tasked with analyzing traffic, interface counters, and other relevant events that may make traffic suspicious (frequent changes in route advertisements, a large number of ICMP (for "Internet Control Message Protocol") error messages, or others) and then determining whether assistance is required from a mitigation server, in the event of attack detection (proven or not).

[0074] It should be noted that an agent can be embedded in a network node affected by an ongoing attack. Similarly, the agent can detect an attack that affects another node in the network. The node that detected the attack may or may not be involved in the execution of the mitigation plan.

[0075] It is recalled that within the meaning of the invention, a node requiring mitigation intervention is a node typically identified in a mitigation plan as being the target, the source or the collateral victim of an attack, or a node involved in the implementation of this mitigation plan (for example, by executing a traffic redirection policy, by modifying its routing table).

[0076] The network therefore requests SOS assistance, for example via one of the dedicated ACT-AD security agents it has on board.

[0077] An example of how the assistance request is processed and processed is detailed on the figure 7 . A network agent R1 sends a message named for example SOS (at step S-AM1) to indicate at least one suspected target (for example a node R2, an IP prefix, network resource, or others) to at least one mitigation server SM, here belonging to the network NW. The latter decides after analyzing the request to request at least one mobile mitigation fleet (referred to as "mobile fleet" in the following for the sake of simplification), for example a mobile fleet composed of drones. Several SOS messages can be received by the server SM.

[0078] The SOS message (target, type, etc.) may include the following fields: a "target" field indicating the target concerned by the request. A target can be an IP prefix, an IP address, a node, a list of nodes, a network segment, a network interface, etc. A node is identified by a unique identifier such as an IP address, an alias, a domain name, a geographical location, etc. A network segment is identified by an autonomous system (AS) number (private), an area identifier according to the OSPF (Open Shortest Path First) routing protocol, a geographical location, an alias, etc. In the case where no target is indicated in the SOS message, this can conventionally mean that the source of the SOS message is the target of the attack itself; an optional "type" field which provides the type of attack in progress. The mitigation server can ignore this information.

[0079] Other information may be included in the SOS message such as a network identifier (network_id) or other.

[0080] Upon receipt of this SOS message, the NW network SM mitigation server: decides based on the SOS message to implement (or not to implement) a mitigation plan which will use the resources of the mobile fleet (step S-AM2), and selects, if necessary, a mitigation server of the mobile fleet or in connection with (i.e. connected to) the mobile fleet (referenced MOB-SM on the figure 7 ), at step S-AM3.

[0081] Information to characterize the anomaly as well as the network nodes concerned are then communicated by the SM mitigation server of the NW network to this MOB-SM mitigation server in conjunction with the mobile fleet, in a mitigation request message called here MITIGATE, at step S-AM4.

[0082] This MITIGATE message (network_id, target, type, ...) may include the following fields in particular: a “network_id” field comprising a unique identifier of a network, such as an AS number: this identifier may be required if a mitigation server (respectively the mobile fleet) is in contact with several networks and the identity of the network to which the “target” is connected (or the target is part of the network itself) cannot be deduced from the parameters of the security association used to transmit the request; a “target” field having the same structure as that of the SOS message of step S-AM1: this field may be identical to that received in an SOS message or modified by a mitigation server due to the nature of the attack and additional information available to the mitigation server such as network topology or network monitoring data, for example.This field indicates the network node(s) (respectively, the IP resources (e.g., IP prefix(es)) that require mitigation intervention; a “type” field that provides the type of attack in progress, this information being able to be used in the selection phase of a mobile DPS service. The DPS service is based on the definition and implementation of mitigation plans that exploit in particular fleets of mobile objects in accordance with the invention.

[0083] Other information may be included in this MITIGATE message, such as a mitigation deadline (immediate or delayed, duration of intervention, etc.), or others.

[0084] In the next step S-AM5, the MOB-SM server coordinates (possibly with other members of the mobile fleet) the optimal positioning of the mobile fleet so that at least one of the mobile objects (according to the connection engineering of the mobile fleet to the network, the engineering being able to be derived from the routing policy associated with the mitigation plan) of said fleet can connect to the NW network and the mobile fleet can execute the mitigation actions. To this end, it is noted that it is sufficient for a mobile object to be positioned within radio range of the network node on which it must intervene.

[0085] To obtain the position of network nodes and / or mobile objects, the server may have (locally or via an external entity) a location map of the various objects in the fleet (e.g. GPS coordinates, supported functions, charge, battery status) as well as the location of the nodes (elements) of the protected network. If the network nodes are static, such location is known to the network operator.

[0086] The location map can be populated by the nodes themselves and / or by the objects in the fleet, by reporting their geographical positions. For this purpose, mobile objects can carry a GnSS (Global Navigation Satellite System) receiver that allows them to report their geographical position. Network nodes can advertise their geographical position using the resources of a dynamic routing protocol that they actively use, such as for example for the OSPF protocol the extensions described in the document by A. Lindem et al. entitled "OSPF Extensions for Advertising / Signaling Geo Location Information", October 18, 2017.

[0087] The location map can also be fed by neighboring nodes and / or fleet objects neighboring the affected nodes and objects, which establish adjacency tables for routing purposes. This can be considered, for example, when one of the nodes requiring mitigation intervention is unable to trace its geographical position. The adjacency tables linked to the activation of a dynamic routing protocol provide, for each node (respectively each mobile object), the list of its neighboring nodes and / or its neighboring mobile objects. By implementing a triangulation technique, it is possible, from the geographical position of the neighboring nodes and / or mobile objects neighboring the attacked node, to deduce its geographical position and to dispatch an object from the mobile fleet near this node.

[0088] The mobile fleet thus connects to the network via one or more mobile objects, and according to one of the embodiments described later with reference to the following main step S-RR (“NETWORK_ATTACHMENT”).

[0089] In an alternative implementation of the first main stage S-AM1, a mobile surveillance fleet itself detects an anomaly that requires mitigation actions. Three sub-variants are presented below as examples.

[0090] The first sub-variant assumes that mitigation is provided by the same mobile surveillance fleet. Thus, with reference to the figure 8 , the fleet decides that a mitigation action is necessary because after analyzing the traffic, the MOB-SM mitigation server in connection with this fleet selects at least one mobile object to connect to the NW network. This choice can also result from the decision not to involve another fleet, according to an intervention fleet selection procedure implemented by the MOB-SM mitigation server.

[0091] Information to connect the fleet to the network where the attack was detected is communicated to these objects using a procedure called "grafting".

[0092] The messages associated with the GRAFT procedure (referred to here as GRAFT(network_id, list(object_id, list(peer_id), ...) messages) include the following information: a "network_id" field including the identifier of the network to which a mobile fleet must connect. This identifier is not included in a message if there is no ambiguity in the selection of this network (for example, the objects of a fleet are exclusively dedicated to the mitigation operations of a single network). This information is typically used for the selection and implementation of mechanisms for establishing security associations with this network; a List (object_id, List(peer_id)) field indicating one or more object identifiers (object_id): each object is typically associated with one or more neighbor nodes (designated by peer_id identifiers), a neighbor node designating a node in the network with which a mobile object must connect. An object or neighbor identifier can be structured as an IP address, an alias, a domain name, etc. The object identifier can be omitted if the recipient of the message is the object concerned.The List(object_id, list(peer_id)) information can be omitted if the selection of objects as well as the network connection points (nodes) is implemented in a distributed manner (with a conventionally predefined order) by the fleet objects. A list of objects is inserted if the message is typically intended for a mobile DPS fleet controller which is then responsible for generating messages for the objects concerned. These messages will only include the instructions associated with each object concerned.

[0093] Other information may be included in GRAFT messages such as a connection deadline (immediate or delayed, connection duration, etc.), a geographic area, etc.

[0094] Then, the fleet connects to the network as described further with reference to the next main step S-RR (“NETWORK_ATTACHMENT”).

[0095] A second sub-variant assumes that mitigation is coordinated by a mitigation server external to the monitoring fleet as illustrated in the figure 9 The monitoring fleet decides to contact a SM mitigation server after analyzing the traffic and detecting an anomaly by sending an SOS2 message to this external SM mitigation server. The mitigation server selects a mobile mitigation fleet or at least one drone from a mobile mitigation fleet (POS arrow) to connect to the network where the attack was detected. The information to proceed with the connection of the mitigation fleet or the selected drone to the network is communicated to them using a GRAFT message as mentioned previously. Then, the mobile mitigation fleet connects to the network as described later with reference to the following main step S-RR (“NETWORK_ATTACHMENT”).

[0096] A third sub-variant assumes that mitigation actions are triggered from another mobile mitigation fleet following a mitigation request message received from the monitoring fleet as illustrated in the figure 10 . In the example in this figure, a monitoring fleet is responsible for monitoring, analyzing, and deciding whether to request another mitigation fleet. A SOS2 message similar to that of the figure 9 is sent to a mitigation fleet selected by the monitoring fleet for its capabilities to handle the type of attack observed, according to identification information, location of the intervention and description of the attack, which are communicated to this mitigation fleet by the monitoring fleet (via a GRAFT message as described previously). This mitigation fleet positions itself optimally according to the information communicated in the GRAFT message so that it can connect to the network and carry out mitigation operations. Then the mitigation fleet connects to the network as described further below with reference to the following main step S-RR (“NETWORK_ATTACHMENT”).

[0097] In an alternative embodiment illustrated on the figure 11 , an attack protection service (DPS) decides on the basis of information provided by means other than an SOS message in particular (for example configuration, monitoring report, or other) to request at least one mitigation fleet. The communications procedures and interactions with the network and its components are identical to those presented above.

[0098] In addition, the network, and the fleets that protect it (surveillance and / or mitigation fleets), can be operated by the same operator or by separate operators. figure 6 illustrates some examples of implementation: the DPS service and the network are operated by the same entity and the mitigation is managed by the SM mitigation server of the NW network (Case figure “6D”), or the network supports a local DPS service implementing an SM mitigation server, which interfaces with another external DPS service, implementing a MOB-SM mitigation server linked to the fleet (Case figure “6A” and figure “6C”), or the network exclusively uses a third-party DPS service (Case figure “6B”), without an SM mitigation server of the NW network, other configurations are also possible.

[0099] So, with reference to the figure 25 , the first main S-AM step can be summarized for example as follows: ACT-AD network security agents (active) can identify suspicious traffic. In this case, the ACT-AD agents indicate (possibly, because the mitigation server can also determine this information based on the location of the agent in the network) the nodes of the NW network which are under attack or which are likely to be attacked, the nodes to be protected or sources of an attack in an SOS message to a SM mitigation server known to the active agents, the SM mitigation server decides whether the suspicious traffic is indeed a proven attack, and, if it is not linked to a mobile mitigation fleet, selects a MOB-SM mitigation server linked to (or belonging to) such a mobile fleet, and sends it a mitigation request REQ message which may include some of the data from the SOS message,the MOB-SM mitigation server which is linked to (or belonging to) the mobile mitigation fleet then triggers the mitigation operation and defines in particular, based on the data of the REQ message, the appropriate mobile objects (e.g. drones) and appropriate positions POS of these mobile objects relative to the nodes of the NW network attacked and / or to be protected (nodes to be protected can typically be strategic nodes of the NW network), the MOB-SM mitigation server which is linked to (or belonging to) the mobile mitigation fleet then sends (directly or via a controller) one or more GRAFT messages to the aforementioned appropriate mobile objects, these GRAFT messages indicating in particular the positions that the appropriate mobile objects must occupy to connect to one or more target nodes of the network requiring intervention.

[0100] In particular, the geographical position of a mobile object such as a drone connecting to a network node is chosen to be in direct contact (a radio link, for example) with this node without going through an intermediate node which itself risks being attacked.

[0101] Referring again to the figure 25 , a general method within the meaning of the invention may also comprise a second general step of connection to the S-RR network, for example. This is a step of connection to the network because, in order to implement mitigation actions, a fleet of mobile objects can be dispatched to the area and connect to the network according to one of the two modes described below.

[0102] The location chosen on the network to connect the fleet takes into account several criteria such as: be as close as possible to the source of an attack, be as close as possible to a victim of the attack, protect a strategic node, or other.

[0103] These criteria can be taken into account for identification: (1) the network node(s) that require mitigation intervention and (2) the routing policy of the mitigation plan.

[0104] The GRAFT message (presented previously) is used to communicate to a mobile object the order to connect to a network, while a message named CEASE (network_id, list(local_node_id, list(peer_id)), ...) is used to order an object to disconnect from a network, as will be seen later in particular with reference to the S-DESAC step.

[0105] The arguments recorded in a CEASE message are similar to those of a GRAFT message but nevertheless: This message can be sent to or from any network node and this message only concerns disconnection operations.

[0106] Furthermore, a message named POLICY is used to communicate to an object a set of instructions characteristic of the implementation of mitigation measures adapted to the nature of the attack. This could be, for example: an order to the mobile object to move to a new position, to perform specific processing (e.g., marking, conditioning, destruction, etc.) of all or part of the traffic redirected via the fleet, to add an entry in a FIB (“Forwarding Information Base”) or a RIB (“Routing Information Base”) maintained by the network nodes and / or the mobile objects. Such tables allow the nodes and mobile objects to record, in particular, the routes that allow traffic to be routed to a particular destination, to order an activation or an update of an ACL (“Access Control List”) filter, etc.

[0107] The POLICY message can also be used to interact with network nodes from the fleet.

[0108] The structure of the POLICY(network_id, list(object_id, list(action)), ...) message is based on the following information: a "network_id" field that has the same meaning as the "network_id" field recorded in the GRAFT message. This information is not necessary when the POLICY message is intended for a network node or a mobile object connected to a single network. a list(object_id, list(action)) field indicates one or more object identifiers (object_id); each object is typically associated with one or more mitigation actions. A mitigation action can be a filtering rule, installation of an entry in the FIB / RIB, configuration of a traffic load balancing policy, new positioning, etc. An object identifier can be structured as an IP address, an alias, a domain name, etc. The object identifier can be omitted if the recipient of the message is the affected object.A list of objects is inserted if the message is typically intended for a mobile DPS fleet controller which is then responsible for generating the messages intended for the objects concerned (and these messages only include the instructions associated with each object, for example).

[0109] Other information / instructions may be included in the POLICY message, such as a policy enforcement deadline (immediate or deferred, etc.).

[0110] The examples below assume that the mitigation actions consist of an extension of the capacity of a network node (i.e. of its resources), or even a partial bypass of a node or a network segment. However, the connection modes apply to other types of mitigation actions such as those described in the general main step S-ACT of the figure 25 (relating to “ACTIONS_MITIGATION”).

[0111] The capacity extension can be local or “parallel” (also called “bypass” below).

[0112] In the local extension mode, the connection of the mitigation fleet to the network is performed locally by the node identified in the connection order transmitted by the mitigation server in a GRAFT message.

[0113] After identifying an incident that requires the intervention of a fleet of mobile objects to initiate mitigation actions, a command (GRAFT) is transmitted to the fleet by the mitigation server to position itself in the affected area, if necessary. Then, the fleet connects to the network element indicated in the GRAFT message. Information to establish secure communication (e.g., certificates, secrets, hashes, encryption algorithms, etc.) between the node and the fleet can also be communicated via secure channels.The orders communicated to one or more mobile objects to position themselves in the area concerned, as well as the orders communicated to one or more mobile objects to connect to the network can be formulated directly by the fleet (for example by a mitigation server embedded within the fleet) following the detection of an anomaly, or formulated upon receipt of a MITIGATE or SOS or SOS2 message sent by one of the network nodes.

[0114] Once the network connection is established, and with reference to the example of the figure 12 , the fleet of mobile objects (i.e. drones here) is considered as a capacity extension (memory, processing means (processor, working memory, etc.), bandwidth, or others) of the suspected network node (referenced “R2” in the figures where it is represented).

[0115] Several strategies can thus be adopted for the distribution of traffic between the node "R2" and its extension provided by the mobile mitigation fleet. These strategies can be configured in advance on R2 by the network operator in the form of policies (of the ECA ("Event - Condition - Action") type, for example). This could be, for example: of an "event" such as exceeding a traffic threshold on one of R2's interfaces, of a "condition" defined based on the destination address of the traffic, and of an "action" consisting of redirecting the associated traffic to the fleet of mobile objects.

[0116] These policies are then communicated by the fleet of mobile objects to R2 during the S-RR connection step via the POLICY message.

[0117] During mitigation operations, traffic may be processed locally at "R2" or redirected in whole or in part to the mobile object fleet for processing. The redirection is local to R2 (e.g., according to "Match-Action" instructions, following a load distribution of x% via R2 and (100-x)% via the fleet). The following example illustrates an ECA rule where R2 is instructed, possibly using the POLICY message, to redirect all traffic destined for an attack target with identifier "1.2.3.0 / 24" to the fleet. “Event”: Activation-Interface-Flotte { { “Condition”: Dest_Prefix=1.2.3.0 / 24, “Action”: Redirect-via-Flotte_any}}

[0118] One or more mobile objects may be requested when traffic is redirected to a fleet of mobile objects. The selection of the mobile object ("ingress", entry point into the fleet) may be carried out by the R2 element in several modes such as those illustrated as examples respectively by the figures 12 et 13 .

[0119] An example of actions communicated to R2 in a POLICY message for the selection of drones to be requested for mitigation operations is given below: “drone1” is chosen if the traffic is destined for node 1.2.3.0 / 24 while “drone2” is chosen for the redirection of traffic destined for node 2.3.4.0 / 24. “Event”: Activation-Interface-Flotte { { “Condition”: Dest_Prefix=1.2.3.0 / 24, “Action”: Redirect-via-Flotte_drone1}, { “Condition”: Dest_Prefix=2.3.4.0 / 24, “Action”: Redirect-via-Flotte_drone2}}

[0120] Once the mitigation action is executed by the fleet, legitimate traffic can for example be rerouted to R2 which then processes it according to the nominal network routing rules.

[0121] In the so-called "parallel" or "bypass" extension mode, the connection of the mitigation fleet to the network is carried out without involving the node that is the victim of an incident or an attack (R2 in the figure 14 , for example). R2 is in this example the attacked node which requires mitigation intervention.

[0122] Thus, after identifying an incident or an attack that requires the intervention of a mitigation fleet to carry out one or more mitigation actions, an order is transmitted to the mitigation fleet by the mitigation server so that it positions itself as close as possible to the area concerned if necessary (via a POLICY message). Then, the fleet connects to the network nodes indicated in the GRAFT message (these nodes are then different from the R2 node attacked and concerned by the mitigation intervention). Typically, two nodes (ingress, egress) are indicated per traffic direction (for "incoming" and "outgoing"). The same entry and exit nodes can be indicated for both directions (and thus the entry node for outgoing traffic is considered as the exit node for incoming traffic). With reference to the example of the figure 14 , the two input and output nodes are R1 and R4 respectively.

[0123] Once the connection of the mitigation fleet to the network is effective (in other words here between the mitigation fleet and the nodes (ingress, egress) R1 and R4), and with reference to the example of the figure 14 , the fleet of mobile objects is seen as a capacity extension of the “R2” node which suffered the attack and required intervention.

[0124] Several strategies can be adopted by R1 and R4 for the distribution of traffic between "R2" and its extension (from the mobile object fleet), depending on the nature of the mitigation action to be performed for example. These strategies can be configured in advance on R1 and R4 by the network operator in the form of ECA ("Event Condition Action") policies, communicated by the mobile object fleet to R1 and R4 using POLICY messages. During mitigation operations, traffic can be sent directly to "R2" or be redirected to the mobile object fleet for processing. The redirection is local to R1 and R4 (for example, according to "Match-Action" instructions, indicating a load distribution of x% via R2 and (100-x)% via the fleet).

[0125] The following configuration shows an example of policies communicated to R4 for selecting inbound traffic to be redirected to the fleet for mitigation purposes: all UDP traffic destined for the 1.2.3.0 / 24 prefix and having a port number of 443 is redirected to the fleet; the rest of the traffic is routed according to the nominal route. Other strategies may be adopted by R1 and R4 depending on the nature of the attack. “Event”: Activation-Interface-Flotte { { “Condition”: { “Dest_Prefix” =1.2.3.0 / 24, “Protocol” = udp, “Dest_Port_number” = 443}, “Action”: Redirect-via-Flotte_any}}

[0126] Additionally, the following configuration shows the example of policies communicated to R1 for selecting outbound traffic to be redirected to the fleet for mitigation actions: All UDP traffic originating from the 1.2.3.0 / 24 prefix is ​​redirected to the fleet; the rest of the traffic is routed according to the nominal route. “Event”: Activation-Interface-Flotte { { “Condition”: { “Src_Prefix” =1.2.3.0 / 24, “Protocol” = udp}, “Action”: Redirect-via-Flotte_any}}

[0127] One or more mobile objects may be requested when traffic is redirected to a fleet of mobile objects. The selection of the "ingress" mobile object (for entry point) may be performed by nodes R1 and R4 in several ways similar to those of R2 illustrated by any of the figures 12 et 13 .

[0128] In the context of capacity expansion, once the processing is done by the fleet, the traffic is rerouted to R2 which then processes it according to the nominal routing rules of the network. Other actions can be applied (typically: blocking the traffic).

[0129] So, with reference to the figure 25 , the main S-RR step can be summarized for example as follows: a drone i, positioned near a node Rj (thanks to the GRAFT message received from the mitigation server), can offer this node Rj additional resources corresponding to a “capacity extension” (EXT CAPA), by connecting: * directly to this node Rj, in local extension mode, or, * to one or more neighboring nodes of this node Rj, in parallel or bypass mode (two nodes R1 and R4 in the example of the figure 14 , or even a single node in a particular case of figures 20-21 ) without being connected to this node Rj; once connected (CONNECT) to this node Rj, the drone i can secure the exchanges by encrypting them (SECUR), in accordance with the policy previously defined by the POLICY messages; in fact, the MOB-SM mitigation server in connection with (or embedded in) the fleet previously sends POLICY messages: * to the mobile objects of the fleet which intervene to protect the NW network (in addition to the GRAFT messages), and * to the nodes Rn,..., Rk remaining active in the NW network, in order to define the appropriate traffic rules for mitigating the attack (these rules can be defined by ECA policies each adapted to a mobile object or to a node or to a set of mobile objects and nodes).

[0130] In reference to the figure 25 , for the implementation of the following general step S-ACT, of setting up mitigation actions (ACTIONS_MITIGATION), several variants are possible. Indeed, for the application of the mitigation service by a fleet of mobile objects, the policies for connecting fleets of mobile objects to the network described previously are not recalled here. Also, the examples relating to capacity extension are not illustrated.

[0131] There figure 15 illustrates the example of a mitigation action which consists of replacing a network node which is subject to an attack (referenced R3 on the figure 15 ). A mobile object (e.g., a drone) in a mitigation fleet has been ordered to connect as described above. This is how it establishes connections with all of R3's neighbors. POLICY messages are then sent to R1, R4, R5, and R6 to redirect traffic to this mobile object and disable their communication interfaces to R3. In doing so, a software update, the installation of a security patch, etc. can be performed while preserving service continuity (legitimate traffic is rerouted to the mobile object while the failed node R3 is restored to its normal operation). In some cases, the mitigation intervention on R3 can be performed via the mobile object itself. In this case, the mobile object also connects to R3; this order is received via a POLICY message (and not via the GRAFT message).

[0132] The example of the figure 16 illustrates another example of mitigation action and more specifically the activation of a policy for intercepting suspicious traffic as close as possible to the source of the DDoS attack. Thus, all or part of the traffic is redirected to the fleet of mobile objects which incorporates DDoS inspection and mitigation functions. These functions can be distributed among several mobile objects (e.g. drones). Non-suspect traffic is reinjected into the nominal network while DDoS traffic is deleted. Metadata characteristic of the attack are recorded by the fleet for later analysis of the dynamics of the attack (amplitude, duration, type of traffic, etc.) and to define the preventive measures to be applied to prevent similar attacks from occurring again on the network. Legitimate traffic is injected by attaching itself to the same node or to a different network node than the one used to intercept the traffic.The selection of the node to reinject the legitimate "egress" traffic (exit node) is a fleet decision which takes into account the load of the node having suffered the DDoS attack (for example), the compensation of the processing delay within a DPS mitigation server in connection with the mobile fleet or even the number of IP hops of the nominal path (as illustrated as an example on the . figure 17 , where the number of hops of the nominal path: four (R1-R2-R4-R6), is identical to that used via the mobile fleet (R1- two drone hops -R6)), etc.

[0133] Another variation is illustrated on the figure 18 where two fleets of mobile objects (drones) are involved to process and route legitimate traffic. This variant can be implemented, for example, when several nodes in a network have suffered an attack (infection of an operating system (or OS for Operating System) for example). In doing so, the network operator gives itself the necessary time for investigation and application of patches without interruption of service.

[0134] There figure 19 illustrates yet another variant in which traffic selection policies are programmed into a network node. Legitimate traffic is routed according to the nominal rules, while suspicious traffic is redirected to a fleet of mobile objects (drones) which is responsible for analyzing it and blocking the DDoS traffic. In addition to ensuring service continuity, this variant has the advantage of optimizing the use of network resources because the DDoS traffic is not routed through this network but blocked "upstream."

[0135] THE figures 20 And 21 show examples of policies applied to inbound or outbound traffic to bypass one or more network nodes following a denial of service attack generated by a node located in the network to be protected. The fleet of mobile objects is tasked with intercepting legitimate traffic and routing it to the Internet network ( figure 20 , outgoing traffic) or to machines connected to the NW network ( figure 21 , incoming traffic). Interception of incoming traffic assumes that specific routes are advertised by the fleet of mobile objects and noted NW# to be able to receive traffic intended for the target NW network or the latter NW network does not advertise these routes to its neighbors. These routes are therefore more specific than those advertised by the NW network to guarantee their selection.

[0136] In reference to the figure 25 , the S-ACT step can then be summarized for example as follows. The mobile objects involved ensure that: the suspicious DDoS traffic is blocked and filtered for example, and / or that the concerned nodes (suspected and / or to be protected) Rj of the NW network are rescued for example (in bypass mode or other), the nominal traffic can continue to be routed securely (reference "Root traffic name" of the figure 25 at the S-ACT stage.)

[0137] In reference to the figure 25 , the next general step S-DESAC aims for example at a disconnection (DESACTIVATION) to terminate the mitigation operations via a mitigation fleet. Several variants are possible to terminate the mitigation operations undertaken by a fleet and to disconnect this fleet from the network to be protected. The CEASE and POLICY messages introduced previously are used for this purpose.

[0138] In the embodiment described here, the ACT-AD security agents embedded in the network decide after analyzing the traffic that the attack is no longer active. One of these agents contacts, for example, the MOB-SM mitigation server linked to or embedded in the fleet to ask it to end the mitigation operations and to disconnect (via a CEASE message). The MOB-SM mitigation server can accept the request immediately or request to keep the mitigation action active for an additional period because the mitigation fleet still detects DDoS traffic in the analyzed traffic. A message named, for example, WAIT (reason, timer, ...) is then sent by the fleet to said agent, with the following fields: a “reason” field indicating the reason why the disconnection request must be deferred, and a “timer” field indicating a deadline beyond which the same request can be resent, with mitigation operations being maintained in the meantime.

[0139] After analyzing the traffic redirected to the mobile fleet, the latter can decide to coordinate the disconnection of the service with the protected network. To do this, the MOB-SM mitigation server communicates, for example, to the ingress / egress nodes of the network the new policies for handling suspicious traffic in a POLICY message. An example of a policy is described below where all UDP traffic from 1.2.3.0 / 24 can now be routed along the nominal path, as follows: “Event”: Deactivation-Interface-Flotte{ { “Condition”: { “Src_Prefix” =1.2.3.0 / 24, “Protocol” = udp}, “Action”: local_default_forwarding}}

[0140] After activating the new policies, the nodes in the protected network and those in the fleet disconnect. The mobile objects in the fleet disconnect after receiving a CEASE message.

[0141] In reference to the figure 25 , this last main S-DESAC step can therefore be summarized for example as follows: one of the ACT-AD network security agents may determine that the attack is no longer active and contact the MOB-SM mitigation server in conjunction with (or embedded in) the fleet to terminate the mitigation; the MOB-SM mitigation server in conjunction with (or embedded in) the fleet checks whether the attack is still active (e.g. by probing the mobile objects involved in the mitigation intervention to determine whether they are still detecting suspicious traffic, by consulting the progress of the execution of a scrubbing function), and if so, sends a WAIT message to the ACT-AD security agent, and otherwise sends a CEASE message to the mobile objects involved in the intervention (or, prior to this step, sends POLICY messages describing the traffic management policies aimed at gradually ceasing the routing of traffic by the mobile objects).

[0142] THE figures 22 and following summarize the messages exchanged between the different entities in the entire process above.

[0143] In the particular example of the figure 22 , we assume that an ACT-AD security agent is the initiator of the mitigation request. This agent sends an SOS message to the SM mitigation server (located in the NW network or outside, as seen previously). This SM mitigation server decides to request a mobile DPS service by sending a mitigation request message to one of the MOB-SM mitigation servers of the mobile DPS service, in the illustrated example. One of these servers handles the request and decides to connect a mobile fleet to the NW network using several mobile objects, in this case several drones (Drone#1, ...Drone#i); connection instructions are communicated to these drones using GRAFT messages. Similarly, this MOB-SM mitigation server decides on the repositioning actions of certain drones or even configuration modifications. POLICY messages are sent to all or some of the drones of the mitigation fleet (Drone#j, ...Drone#k).Note that some drones in the first group (Drone#1, ...Drone#i) can also receive POLICY messages. There is no constraint on the order in which POLICY and GRAFT messages are sent. Once the connection with the NW network is established, the MOB-SM mitigation server can communicate instructions to the nodes R1,.., Rs of this NW network. Depending on the attack progress and the mitigation actions, the mitigation server can decide on new mitigation actions to be executed by the objects in the fleet or the nodes in the protected network. The mitigation server can terminate the procedure by ordering the drones (Drone#1, ... Drone#i) to disconnect from the network using CEASE messages.

[0144] Unlike the example of the figure 22 , the example of the figure 23 assumes that the MOB-SM mitigation server that receives the SOS message is the one that is able to decide which drones should connect to the network, which should reposition themselves, etc. The rest of the operations are identical to those of the figure 22 .

[0145] Orders transmitted to a fleet of mobile objects by a mitigation server can be sent individually to the mobile objects of a fleet or be relayed by a fleet controller CTRL which is also one of the mobile objects of the fleet. This implementation is illustrated by the figure 24 . The instructions sent to the CTRL controller can be aggregated like the GRAFT message (typically instructions targeting several mobile objects being communicated in the same message) or not (like POLICY messages). In this case, the controller is responsible for extracting (and completing) the instructions relating to each mobile object. The exchanges upstream of the MOB-SM mitigation server can be similar to those exchanged upstream of the MOB-SM server of the figure 22 or those exchanged upstream of the MOB-SM server of the figure 23 .

Claims

1. Method for managing assistance for a communication network (NW) capable of routing traffic characteristic of a computer attack, the method comprising: - upon detecting a computer attack, identifying at least one first node (R2) of the network, requiring a mitigation intervention, and identifying a traffic routing policy in the network; - controlling a movement of at least one mobile object (F) comprising at least one communication interface, so as to connect the mobile object to at least one second node (R2; R1, R4) of the network determined relative to the first node according to said traffic routing policy; and - controlling at least one portion of the traffic routed by the network, so as to redirect said portion of the traffic to the mobile object via at least said second node of said network.

2. Method according to Claim 1, wherein the second node corresponds to the first node (R2).

3. Method according to any of the preceding claims, wherein a plurality of mobile objects (F; F1, F2, F3) is provided, each comprising at least one communication interface for communicating at least between mobile objects, and a first mobile object, from among said plurality of mobile objects, is controlled so as to connect to at least said second node of the network.

4. Method according to Claim 3, wherein identifying the first node of the network and the traffic routing policy in the network is carried out by a mitigation server (SM-MOB) embedded in one of the mobile objects.

5. Method according to any of Claims 3 and 4, wherein the computer attack is detected by a second mobile object (ACT-AD) connected to the network.

6. Method according to any of the preceding claims, wherein the computer attack is detected by the mobile object, which is controlled so as to connect at least to said second node.

7. Method according to any of Claims 1 to 4, wherein the computer attack is detected by a third node of the network.

8. Method according to any of the preceding claims, wherein the mobile object is equipped with a processing circuit comprising computing resources providing computing capabilities for processing at least said portion of the traffic redirected to the mobile object.

9. Method according to any of the preceding claims, wherein the mobile object is configured to analyse and filter at least said portion of the traffic redirected to the mobile object.

10. Method according to any of the preceding claims, wherein the required intervention is traffic mitigation (MITIGATE) in response to a denial of service attack.

11. Method according to any of the preceding claims, wherein the mobile object is configured to establish communication via a radiofrequency link in order to connect to at least said second node, with the movement of the mobile object being remotely controllable so as to approach a geographical position of the second node.

12. Method according to any of the preceding claims, comprising: - transmitting a graft message (GRAFT) to the mobile object, in order to control a movement of the mobile object and to connect the mobile object to the second node, designated in the graft message; - transmitting a routing policy message (ROUTING) to the mobile object, in order to control at least one rule for routing traffic via the mobile object; and - transmitting a routing policy message (POLICY) to at least the second node, in order to control at least one rule for routing traffic via the second node.

13. Method according to Claim 12, wherein said messages are transmitted by at least one mitigation server (SM-MOB) linked to the mobile object.

14. Computer program, comprising instructions for implementing the method according to any of Claims 1 to 13, when said instructions are executed by a processor of a processing circuit.

15. System for managing assistance for a communication network capable of routing traffic characteristic of a computer attack, the system comprising at least: - a mobile object (F) comprising at least one communication interface for connecting to at least one node (R2) of the network; - a mitigation server (SM-MOB; SM) configured, in response to the detection of a computer attack, to: * identify at least one first node of the network, requiring a mitigation intervention; * identify a traffic routing policy in the network; * control a movement of the mobile object so as to connect the mobile object to at least one second node (R2; R1, R4) of the network determined relative to the first node according to said traffic routing policy; * control at least one portion of the traffic routed by the network, so as to redirect said portion of the traffic to the mobile object via at least said second node of said network.

16. Mitigation server for assisting a communication network capable of routing traffic characteristic of a computer attack, the mitigation server being configured, in response to the detection of a computer attack, to: * identify at least one first node (R2) of the network, requiring a mitigation intervention; * identify a traffic routing policy in the network; * control a movement of at least one mobile object (F) comprising at least one communication interface, so as to connect said mobile object to at least one second node (R2; R1, R4) of the network determined relative to the first node according to said traffic routing policy; * control at least one portion of the traffic routed by the network, so as to redirect said portion of the traffic to the mobile object via at least said second node of said network.