NAT Detection via Authenticated Operations
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Solution Overview
Problem
Conventional rate limiting systems struggle to effectively manage Network Address Translation (NAT) systems, as they cannot reliably identify the number of users behind a single IP address, leading to either ineffective deterrence of denial of service attacks or unjust blocking of legitimate users.
Innovation Solution
Implementing a system that detects highly authenticated operations from multiple users at individual IP addresses to identify NAT systems, estimating the number of users behind them, and dynamically adjusting rate limiting policies to account for multiple users behind a single IP address.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rate limiting threshold is set high to allow NAT users, then legitimate users are not blocked, but denial of service attacks are not deterred
Solution Approach 1:
The system segments the single IP address into multiple virtual user identities by detecting highly authenticated operations from different users behind NAT. Each user is identified and tracked separately, allowing rate limiting to be applied per-user rather than per-IP-address, thus protecting against DoS attacks while allowing legitimate NAT users to access the service
Solution Approach 2:
The system introduces an intermediary authentication detection mechanism that sits between the IP address and the rate limiting system. This intermediary detects and counts the number of unique users behind each IP address by monitoring highly authenticated operations, then uses this information to dynamically adjust rate limiting thresholds, resolving the contradiction between protecting against attacks and allowing legitimate users
2Reliability
If rate limiting threshold is set low to prevent attacks, then denial of service attacks are deterred, but legitimate users are blocked
Solution Approach 1:
The system makes the rate limiting threshold dynamic by continuously monitoring and adjusting it based on the detected number of users behind each IP address. For IP addresses with multiple legitimate users (detected through highly authenticated operations), the threshold is automatically increased. For IP addresses showing attack patterns, the threshold remains low or blocking is applied. This dynamic adjustment resolves the contradiction by adapting the threshold to the actual usage scenario
3Device complexity
If conventional rate limiting is applied to NAT IP addresses, then implementation is simple, but accurate user identification is lost
Solution Approach 1:
The system uses the highly authenticated operations that users already perform as part of normal service usage to automatically identify and count users behind NAT. The authentication mechanisms (two-factor authentication, identity proofing, etc.) that users already engage with are leveraged to generate the data needed for user identification, eliminating the need for separate complex identification infrastructure while maintaining simplicity in rate limiting implementation
Data Source
AI summary
NAT systems are identified by detecting highly authenticated operations being made by multiple users from IP addresses. Users of a web service are authenticated in response to performing highly authenticated operations, such as identity proofing or multifactor authentication. Successful highly authenticated operations are tracked. A NAT system operating in conjunction with a specific IP address is identified, in response to a threshold number of different users successfully performing highly authenticated operations from the specific IP address within a specific amount of time. The total number of users behind the identified NAT system is estimated, based on the rate at which different users successfully perform operations from the specific IP address. One or more additional action(s) are taken to manage the processing of traffic originating from the specific IP address, taking into account that multiple users are operating behind the identified NAT system. An example action is rate limiting.