VLR (Visitor Location Register)

The Visitor Location Register is the 2G/3G database, typically co-located with the MSC, that holds the temporary subscriber profile of every device currently attached to that MSC's service area. It receives a copy of relevant HLR data via MAP and is updated as subscribers move and authenticate. VLR data is highly sensitive (TMSI, IMSI, current cell), and many SS7 location-tracking attacks ultimately aim to extract or correlate VLR information.

Categories: Radio Access NetworkCore NetworkSignaling

VLR in context

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

The mobile core carries subscriber sessions, mobility and policy. 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.

To place VLR in the wider telecom-security picture, review 5G SA, AMF, Base Station (BS), Capacity Planning, CAPEX and CSCF — each entry cross-references back to this page so you can walk the topic in either direction.

Related terms

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