Gameitall 
On Christmas Day, Valve suffered a major security lapse which a large amount of user’s personal information exposed to other users. The root of the problem was caused by a DDoS (Denial of Service) attack and a caching issue that left over 34,000 people vulnerable.
“The content of these requests varied by page, but some pages included a Steam user’s billing address, the last four digits of their Steam Guard phone number, their purchase history, the last two digits of their credit card number, and/or their email address,” Valve said in a statement. “These cached requests did not include full credit card numbers, user passwords, or enough data to allow logging in as or completing a transaction as another user.
“If you did not browse a Steam Store page with your personal information (such as your account page or a checkout page) in this time frame, that information could not have been shown to another user.”
Valve is currently investigating with their caching partner to identify all the Steam users who had been affected by the attack during the 90 minute window on December 25th. Meanwhile Valve has confirmed that no unauthorized actions were allowed on the accounts aside from the viewing of cached page information, however no additional action is required by users.
DDoS attacks are something of a regularity for game companies like Valve, Sony and Microsoft, where the later two have had services shut down for a long period of time due to these sort of attacks. The attack on the Steam server saw a boost of traffic ranging up to 2,000 percent during the Steam sale.
Valve issued a full apology and explained the further steps they’re taking in order to prevent this from happening again.
In response to this specific attack, caching rules managed by a Steam web caching partner were deployed in order to both minimize the impact on Steam Store servers and continue to route legitimate user traffic. During the second wave of this attack, a second caching configuration was deployed that incorrectly cached web traffic for authenticated users. This configuration error resulted in some users seeing Steam Store responses which were generated for other users. Incorrect Store responses varied from users seeing the front page of the Store displayed in the wrong language, to seeing the account page of another user.
Once this error was identified, the Steam Store was shut down and a new caching configuration was deployed. The Steam Store remained down until we had reviewed all caching configurations, and we received confirmation that the latest configurations had been deployed to all partner servers and that all cached data on edge servers had been purged.
We will continue to work with our web caching partner to identify affected users and to improve the process used to set caching rules going forward. We apologize to everyone whose personal information was exposed by this error, and for interruption of Steam Store service.
