Provide Subscriber Information (PSI)

Provide Subscriber Information is a MAP operation that lets an authorised network element retrieve subscriber data from the HLR or VLR, including current cell, IMEI, and supplementary-service status. While legitimately used by an operator's own elements, abusive PSI from interconnect is a classic SS7 location-tracking primitive, and is filtered as a Category 2 message by FS.11-compliant SS7 firewalls, accepted only from the subscriber's current visited network.

Categories: Radio Access NetworkCore NetworkSignaling

Provide Subscriber Information (PSI) in context

The radio access network is the layer where mobile devices attach to the operator's infrastructure. Attacks in this layer include IMSI catching, rogue base stations, downgrade attacks and jamming, and defenses hinge on mutual authentication, integrity-protected signaling and Open RAN supply-chain hygiene.

The mobile core is where subscriber sessions, mobility and policy live. In 4G it is the EPC (MME, HSS, S/PGW); in 5G it is the Service-Based Architecture with AMF, SMF, UPF, AUSF, UDM and the NRF. Core exposure is the difference between a single-subscriber leak and a fleet-wide breach.

To place Provide Subscriber Information (PSI) in the wider telecom-security picture, review IAP, VLR, Location Tracking Attacks, MVNO, SMS Spoofing (Interconnect) and GTP-U.

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