Valve knows that players cheating on Steam is a serious problem, and it's taking action to address that in a few new ways. One is offering a matchmaking service for Counter-Strike: Global Offensive that's only for folks who've linked their phone number to their Steam account, for two-factor authentication purposes, dubbed "Prime." Any cheating inside that space will result in your number being banned. The next step takes the previous one further and goes platform-wide. Because cheaters tend to have multiple Steam accounts (but typically one phone number), any account associated with a phone number flagged for by Valve Anti-Cheat will be banned for three months. Boom.