Gabe Newell, co-founder of Valve, announced that the security of Steam has been compromised.
In an official bulletin, Newell stated that it was discovered on November 6 that Steam forums were defaced, but further investigation showed that it went beyond the forums.
"We learned that intruders obtained access to a Steam database in addition to the forums." said Newell. "This database contained information including user names, hashed and salted passwords, game purchases, email addresses, billing addresses and encrypted credit card information. We do not have evidence that encrypted credit card numbers or personally identifying information were taken by the intruders, or that the protection on credit card numbers or passwords was cracked. We are still investigating."
Steam has for the time being blocked all access to their forums and alerted users they will be required to update their forum passwords once it comes back online.
"While we only know of a few forum accounts that have been compromised, all forum users will be required to change their passwords the next time they login. If you have used your Steam forum password on other accounts you should change those passwords as well.
We do not know of any compromised Steam accounts, so we are not planning to force a change of Steam account passwords (which are separate from forum passwords). However, it wouldn't be a bad idea to change that as well, especially if it is the same as your Steam forum account password."