SIM farm

Hardware holding hundreds of SIM cards to send or receive SMS in bulk, a major source of both supply and abuse in the SMS market.

A SIM farm, also called a SIM bank, is a rack of modems loaded with SIM cards and driven by software. Legitimate uses include supplying receive-only numbers to verification platforms. Illegitimate uses include bulk spam and fraud, which is why several countries restrict the equipment.

Where a provider sources its numbers shapes both the quality of those numbers and the legal exposure that comes with them.

Why carriers and regulators watch them

A farm can push consumer-priced traffic at business volumes, which is the definition of the routes carriers filter. The same equipment is used to send scam messages that appear to come from ordinary mobile numbers, so enforcement has tightened in several markets.

Receiving is treated differently from sending, since a farm that only accepts incoming codes generates none of the spam that the rules target.

The question worth asking a provider

Ask where numbers come from and whether they are used for sending. A provider that sources through carrier agreements and receives only is in a different position from one pushing outbound traffic through the same hardware.

Our own limits are written down in the acceptable use policy, and how to judge an SMS provider covers what a straight answer to that question sounds like.

Receiving is treated differently from sending

Equipment that only accepts incoming messages generates none of the spam that enforcement targets, since nothing leaves it. The rules and the carrier filtering are built around outbound traffic.

That distinction is worth raising with any provider. A receive-only operation supplying verification numbers sits in a different position from one pushing bulk messages through the same modems.