SS7 & Diameter Protocol Vulnerabilities: Telecommunications Core Routing & Location Privacy
Deep dive into Signaling System No. 7: how SendRoutingInfoForSM (SRI-SM) and ProvideSubscriberInfo (PSI) messages expose mobile subscriber location globally.
Signaling System No. 7 (SS7) and its 4G successor Diameter manage call routing, roaming handover, and SMS delivery across global mobile network operators (MNOs).
1. SS7 Signaling Vulnerabilities
Core Signaling Exploits
Because SS7 originally assumed all interconnected telecommunications carriers were trustworthy state-owned entities, it lacks built-in sender authentication. Malicious actors with Global Title (GT) access can query Home Location Registers (HLR) directly.
| SS7 MAP Message | Intended Operational Purpose | Exploitation Risk |
|---|---|---|
| SRI-SM (SendRoutingInfoForSM) | Retrieve MSC/VLR address to route incoming SMS | Obtains target serving Mobile Switching Center (MSC) |
| PSI (ProvideSubscriberInfo) | Query target VLR for current subscriber status | Extracts exact Serving Cell Global Identity (CGI) and Timing Advance |
| AnyTimeInterrogation (ATI) | Location query for specialized network services | Directly requests real-time subscriber GPS/cell coordinates from HLR |
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