Apparently an “anonymous user” posted the login credentials (username and password) of over 10,000 Hotmail accounts on PasteBin.com. Hotmail accounts include @hotmail.com, @msn.com, and @live.com e-mails.
Microsoft, which has confirmed the story, says this is likely the result of a wide spread phishing scam. To help affected users, Microsoft is “taking measures to block access to all of the accounts that were exposed and have resources in place to help those users reclaim their accounts”. Microsoft wants you to fill out a form  to reclaim your account if it was one of the ones hacked.
According to reports, users with the usernames from “ar” to “bl” are the ones affected. So if your Hotmail username is between “ar” and “bl”, expect to be locked out of your account (in which case you should fill out the form ). Even if you are not one of the ones affected, consider refreshing your Hotmail password anyway.
[via ArsTechina ]