SIM Cloning
Creating a duplicate SIM card that shares a legitimate subscriber's identity, allowing the cloner to make calls and receive messages billed to the victim's account.
Also known as: SIM card cloning, SIM duplication, SIM card copying
Last reviewed: 10 June 2026
SIM cloning exploits the cryptographic key stored on every SIM card that authenticates the subscriber to the mobile network. Earlier 2G SIM cards used algorithms vulnerable to an attack that could extract this key value through a limited number of challenge-response queries, enabling the creation of a functional duplicate card. Modern SIM cards use hardened algorithms and limit authentication attempts, making cloning substantially more difficult.
Despite improvements, SIM cloning remains possible through insider access at SIM manufacturers or carriers, physical access to the target SIM card, and acquisition of SIM-card blanks with the target's credentials through corrupt carrier employees. A cloned SIM allows the holder to impersonate the victim on the network, make calls billed to the victim's account, and receive incoming calls and SMS messages.
The consumer risk from SIM cloning is lower than from SIM swapping but non-trivial, especially in regions with weaker SIM security standards. Signs of SIM cloning include unexpected call charges, missed calls the victim never received, or unexplained network disconnections. Report suspected cloning to your carrier immediately.