SIM box fraud and grey routes: indicators carriers can look for

SIM box fraud, also called interconnect bypass, routes international calls through local SIM cards so that they appear as local traffic. The fraudster avoids the international termination rate and keeps the difference. The legitimate operator loses revenue, and callers can receive poor quality or a wrong caller ID.

How it works

A device holding many SIM cards receives international calls over the internet and re-originates them into a local mobile network. To the local operator, the traffic looks like ordinary subscribers calling each other. For wholesale carriers, the concern is being part of a route that carries this traffic, or buying grey routes that cause quality and compliance problems.

Indicators in call records

• Route quality that does not fit its price, for example unusual answer rates or call durations.
• Caller IDs that are missing, changing often or show an unexpected number format.
• Traffic patterns that look uniform or machine-like compared with normal subscriber behaviour.
• A route whose results change sharply, such as a drop in answer rate or call length.

These are indicators, not proof. Confirming SIM box activity usually needs testing, such as test calls, and often cooperation from the destination operator. Detection from call records helps decide where to look.

How to reduce exposure

• Monitor answer rate (ASR) and average call duration (ACD) per route against its own history.
• Check caller ID delivery and quality on routes you terminate or buy.
• Test suspect routes and review supplier terms and prices.
• Keep records of route changes so you can link them to complaints and disputes.

How Smart Gravity Shield approaches grey routes

Smart Gravity Shield watches ASR and ACD by route and customer, and flags drops and shifts as indicators for your team to investigate. It does not claim to prove SIM box activity from call records alone.

Common questions

Is SIM box fraud the same as grey routing?

They are closely related. Grey routes are unofficial routes that may bypass proper interconnect. SIM boxes are one common technique used to do that.

Can call records prove SIM box use?

No. Call records give indicators. Confirmation usually needs test calls and cooperation from the destination network.

This guide is general information, not legal or security advice. Fraud patterns change, and no detection system catches every case.