A5/2 (GSM Weaker Cipher)

A deliberately weakened GSM cipher with lower security margin than A5/1, designed for countries with export restrictions. A5/2 is cryptographically broken and must be removed from networks. If a device can only use A5/2, the network has a critical vulnerability.

Categories: Threats and AttacksInternet and RoutingEncryption and Cryptography

A5/2 in context

Telecom threats range from opportunistic SMS phishing and SIM swap to nation-state grade location tracking. The common thread is that most attacks exploit the inherited trust model of legacy signaling protocols.

Telecom networks depend on Internet-style routing (BGP, DNS, MPLS) for interconnect. Route hijacks and DNS abuse can degrade or intercept signaling, which is why RPKI and DNSSEC are now standard hardening for carrier networks.

To place A5/2 in the wider telecom-security picture, review ASN, BGP, BGP Hijacking, Broadband, CDMA and CGNAT — each entry cross-references back to this page so you can walk the topic in either direction.

Related terms

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