Thousands of hotmail passwords have been hacked and posted online, according to reports.
Microsoft, which owns the popular web-based email system, told BBC News that it was aware of the claims and that it was "investigating the situation".
A report on technology blog neowin.net said that the details of "over 10,000" accounts had been posted to a website.
The blog suggested the accounts had been hacked or had been collected as part of a phishing scheme.
Phishing involves using fake websites to lure people into revealing personal details such as bank accounts or login names and passwords.
Neowin claims the details were posted on 01 October to pastebin.com, a website commonly used by developers to share code.
Although the details have since been removed, the website said it had seen part of the list.
"[We] can confirm the accounts are genuine and most appear to be based in Europe," Tom Warren, a neowin blogger, wrote on the site.
He said that the list included details of Microsoft's Windows Live Hotmail accounts with email addresses ending hotmail.com, msn.com and live.com.
Microsoft said it had "been made aware of the claims that Windows Live IDs and passwords have been made available on the web".
"We're actively investigating the situation and will take appropriate steps as rapidly as possible," a spokesperson said.
Neowin said that it recommended Windows Live Hotmail users to change their "password and security question immediately".
News source: BBC News
The BBC fixed the typo in the meantime. Pity they didn't linkify the URL while they were at it.
Edited by Mephistopheles, 05 October 2009 - 15:12.