Not sure how legit this is but Change your Passwords just in case

[shane]

http://www.behindgames.com/xbox-live-hacked-48-million-users-exposed/

 

Also the hacker posted a list of some users’ s account information (email and password) and upload 6.12GB file for the entire credentials of every Xbox Live user in an nickname;email;password;join date format, It contains nearly confidental-info on around 47 million users, So we recommend you to change your password immediately.

[shane]

Updated:

 

[uPDATE] Following the publication of this story, Microsoft confirmed with GameSpot that Xbox Live has not been hacked.

"Xbox Live has not been hacked," a company representative said. "Microsoft can confirm that there has been no breach to the security of our Xbox Live service."