X3 (LI) (Lawful Interception X3 Interface — Content of Communication)

Also known as: LI X3, X3 LI interface

X3 is the ETSI lawful-interception interface (TS 103 221-2) that carries Content of Communication (CC) — the actual voice, SMS payload, VoLTE/VoNR media or user-plane packets — from the POI/MF to the LEMF. Traffic is framed with correlation identifiers matching X2 IRI events and is protected in transit inside the LI network.

Categories: Threats and AttacksProtocols and StandardsRegulation and Compliance

X3 (LI) 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 security is written into standards from 3GPP, GSMA, ETSI, IETF and ITU-T. Understanding which body owns which specification, and how they interlock, is essential for both design and audit work.

To place X3 (LI) in the wider telecom-security picture, review ETSI TS 103 221, X2 (LI), Attack Surface Mapping, BGP, Cipher Downgrade Attack and DDoS — each entry cross-references back to this page so you can walk the topic in either direction.

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