Microsoft have issued a service alert to all Xbox 360 users, warning them of possible phishing scams and suspicious messages that come through a Modern Warfare 2 exploit. They previously released a statement on the problem, looks like it still isn't fixed.
"Users may receive potential phishing attempts via title specific messaging while playing Modern Warfare 2," reads the Xbox Live Status site, "We are aware of the problem and are working to resolve the issue. We apologize for any inconvenience this may cause and thank you for your patience."
Apparently, some Xbox Live users have claimed that their Modern Warfare 2 in-game rank and data were altered by other users asking for money. It's not the first phishing scam to hit Xbox Live users, simply be wary of any suspicious messages and don't give out your personal information.
Source: The Escapist