SIM Box Fraud

A SIM box (also called a GSM gateway) is a piece of hardware containing dozens or hundreds of SIM cards. Fraudsters purchase international call-termination minutes cheaply from carriers and then route those calls through the SIM box, which terminates them locally as if each call originated within the country. The destination carrier never collects its legitimate international termination fee; instead the SIM box operator pockets the difference between what was paid for bulk termination and what the legitimate rate would have been.

SIM box operators obtain large quantities of SIM cards, often using stolen identities or buying them from corrupt retail outlets. The fraud also harms consumers because calls terminated through SIM boxes may suffer degraded quality, and the stolen termination revenue ultimately raises prices for legitimate users. Regulatory bodies in many countries mandate SIM registration specifically to reduce SIM box operations.

SIM box fraud is also a gateway to other crimes. The large supply of active SIM cards and the connectivity infrastructure are frequently used for smishing campaigns, robocalling operations, and account takeover attacks that require phone-number verification. Regulators combat SIM boxes using traffic-analysis tools that detect the characteristic calling patterns of a gateway device.