Lawful Interception Concealment via CDR Suppression
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Solution Overview
Problem
In lawful interception scenarios, network operators may inadvertently generate Charging Data Records (CDRs) for monitoring call legs, revealing the presence of interception, even when communication data is routed through an intermediate Mobile Switching Center (MSS), compromising the stealth of the interception.
Innovation Solution
Incorporating a preconfigured identifier for lawful interception in the Called Party Subaddress field of initial address messages, which is propagated through all MSSs, including transit MSSs, allowing these centers to detect and suppress CDR generation for monitoring call legs, thereby concealing the interception from network operators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If monitoring call legs are established for lawful interception, then law enforcement authorities can intercept communications, but Charging Data Records are generated that reveal the presence of interception to network operators
Solution Approach 1:
The patent introduces a special CDR record type with a distinctive operator ID as an intermediary mechanism. This mediator allows the monitoring call leg to function for lawful interception while the special record type prevents normal CDR generation that would reveal interception to operators. The intermediary CDR type acts as a buffer between the interception function and the operator's billing system.
Solution Approach 2:
The patent applies local quality by creating a specialized CDR record with unique properties (special operator ID) that differs from normal CDR records. This local differentiation allows the system to handle monitoring call legs differently from regular calls, suppressing normal CDR generation only for interception-related traffic while maintaining normal billing for regular calls.
2Loss of information
If CDR generation is suppressed for monitoring call legs, then interception remains concealed from operators, but normal billing records may be affected
Solution Approach 1:
The patent uses local quality by applying CDR suppression only to monitoring call legs identified by the presence of a special operator ID in the Called Party Subaddress field. Normal calls without this identifier continue to generate CDRs as usual, ensuring billing operations are unaffected while interception remains concealed.
3Loss of information
If identifier propagation is implemented through all MSSs, then transit MSSs can detect and suppress CDR generation, but message complexity increases
Solution Approach 1:
The patent implements universality by using the existing Called Party Subaddress field in the Initial Address Message to carry the operator ID identifier. This field already serves universal purposes in call routing and identification, so adding the operator ID for interception detection reuses existing message infrastructure without creating new complex message structures.
Data Source
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AI summary
Methods, computer program products and apparatuses enabling to conceal lawful interception from network operators by suppressing the generation of the corresponding Call Detailed Record, CDR. The present invention proposes to conceal interception from network operators by receiving a setup message to set up a monitoring connection towards another entity (e.g. an ISUP IAM), analyze the received setup message, and responsive thereto, establish the monitoring connection towards said another entity, wherein the control unit is further configured to confirm that a preconfigured identifier representative for a lawful interception is included within said setup message (e.g. inside the field Called Party Subaddress, under Operator ID - octets 4, 5 and 6), and responsive thereto, suppress at least partially a generation of data records for said monitoring connection.