CSFB (Circuit-Switched Fallback)

CSFB 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.

Telecom security is written into standards from 3GPP, GSMA, ETSI, IETF and ITU-T. Understanding which body owns which specification, and how the specs interlock (for example 3GPP TS 33.501 with GSMA FS.34 for 5G SBA security), is essential for both design and audit work.

To place CSFB in the wider telecom-security picture, review 5G, MTSI, 6G, Jitter, LEO and LTE-Advanced (LTE-A).

Related terms

• 5G
• MTSI
• 6G
• Jitter
• LEO
• LTE-Advanced (LTE-A)
• MPLS
• NESAS

Equipment

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

• GMSC
• Media Gateway
• MGCF
• MSC
• VLR

Articles in the P1 mobile network security guide

Related topic hubs

• VoLTE Security IMS/VoLTE signaling risk: SIP, IMS-AKA, media plane attacks.
• IMS Security Training Training on IMS, VoLTE/VoNR, SIP and RCS security.
• LTE Security Training Training on 4G/LTE core, Diameter, NAS and RRC security.
• Diameter Security 4G/LTE Diameter threats across IPX/roaming and DEA defenses.

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.