If you think fake base stations are 'only' used as IMSI-catchers by law enforcment agencies and spies, this one will wake you up: This week, The Register reported that 1500 people have been arrested in China for sending spam SMS messages over fake base stations. As there is ample proof available how easy it is to build a GSM base station with the required software behind it to make it look like a real network I tend to believe that the story is not an early April fool's day joke. Fascinating and frightning at the same time. One more reason to keep my phone switched to 3G-only mode as in UMTS, mutual authentication of network and device prevent this from working.