VLR (Visitor Location Register)

VLR 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 VLR in the wider telecom-security picture, review Location Tracking Attacks, NRF, Provide Subscriber Information (PSI), HLR, IAP and Service-Based Architecture (SBA) Security.

Related terms

• Location Tracking Attacks
• NRF
• Provide Subscriber Information (PSI)
• HLR
• IAP
• Service-Based Architecture (SBA) Security
• TEID
• IMS-AKA

Equipment

Circuit-switched core (MSC, MSC-S, VLR, GMSC, MGW)

• CSFB
• GMSC
• Media Gateway
• MGCF
• MSC

Articles in the P1 mobile network security guide

Related topic hubs

• SS7 Security SS7/MAP/CAP/SCCP attacks and defenses across 2G/3G interconnect.
• SS7 Firewall GSMA FS.11 category 1/2/3 SS7 message screening at the STP edge.
• Signaling Firewall Unified SS7/Diameter/GTP/SMS signaling firewall framework.
• SS7 Penetration Testing Interconnect pentest methodology for SS7 signaling.

More from the TelcoSec Glossary

Browse the full TelcoSec Glossary, the Ultimate Guide to Mobile Network Security, or the P1 Arsenal of telecom-security tools.