IMEI (International Mobile Equipment Identity).

A 15-digit number that uniquely identifies a mobile device on a cellular network, allocated by the GSMA and used by carriers to block stolen handsets. It belongs to the Mobile Security category of cybersecurity.

A 15-digit number that uniquely identifies a mobile device on a cellular network, allocated by the GSMA and used by carriers to block stolen handsets.

IMEI is burned into the device's modem and is exchanged with the network during attach so the carrier can authorize the equipment independently from the SIM. The structure includes a Type Allocation Code (TAC) identifying make/model, a serial number, and a checksum. National and regional CEIR (Central Equipment Identity Register) services blacklist IMEIs reported as stolen; legitimate carriers refuse to provide service to blacklisted devices. Although IMEI itself is not an authentication secret, it is sensitive: leaks enable device tracking, fraud against insurance, and reprogramming of cloned phones. Many jurisdictions criminalize IMEI reprogramming, and modern modems make it harder by tying the IMEI to secure-boot-protected modem firmware.

Defences for IMEI (International Mobile Equipment Identity) typically combine technical controls and operational practices, as detailed in the full definition above.

Common alternative names include: IMEI, International Mobile Equipment Identity.