The suspects purchased the SIM card codes for 3 euros each from the phone company employees. These codes were then sold online for 30 euros each, creating bootleg service of sorts. The profits from the ring, estimated at 25,000 euros/month per employee, were placed in off-shore bank accounts.
The year-long investigation revealed that the criminal enterprise had been operating for a decade. An investigator said that the thieves worked for the phone companies, and so were able to operate with impunity. He also added that their network was impressively organized.
Suspicion was initially aroused when SFR, a French carrier, noticed discrepancies in its security system. The fraud also affected the Orange and Bouygues Telecom networks.
source: Yahoo! News