Numerous Twitter users are pointing out that Twitter forced them to change their passwords out of the blue. According to blogger Andrew Girdwood, these users have received an email containing the following message: “Due to concern that your account may have been compromised in a phishing attack that took place off-Twitter, your password was reset,” together with a link for resetting the password.
Although the email itself looks like a phishing attack, it’s genuine; it seems that admins at Twitter have discovered something fishy is going on, and they’re trying to prevent further damage before it happens.
The Next Web also mentions reports that this incident has something to do with the user account @THCx, which may have gained access to a large number of Twitter accounts, possibly by abusing NutshellMail, but all of this is unconfirmed at this point.
[Image Credit: blog.arhg.net]
source : http://mashable.com/2010/02/02/twitter-under-phishing-attack/