Valve issued a formal statement today, December 30, on behalf of Steam’s Christmas day mishap. The statement offers an explanation to the some 35,000 gamers affected by the Denial of Service attack and caching error.
Last Friday, there were a number of users who were greeted by Steam Store pages belonging to other people. This caching error allowed sensitive personal account information stored on Steam to be viewed by unsuspecting users. Some of this leaked information extended to billing addresses, the last four digits of the Steam Guard phone number, purchase history, last two digits of saved credit cards, and email addresses. Apparently, though, none of this information unwittingly provided will allow remote access to a compromised account; as user passwords and credit card numbers were still inaccessible.
In accordance with their web caching partner, Valve promises to notify the affected users once they are identified; however, no further action is required by the end user, because no account altering information was leaked. Valve reports that they are victims of these types of DDoS attacks regularly, but on Christmas day, it exceeded a 2,000 percent increase over the typical Steam traffic. This attack resulted in incorrect code to be initiated which then caused the caching error to occur.
Valve issued a full statement on Steam that can be read here. A summary of how the event happened can be read below.
Early Christmas morning (Pacific Standard Time), the Steam Store was the target of a DoS attack which prevented the serving of store pages to users. Attacks against the Steam Store, and Steam in general, are a regular occurrence that Valve handles both directly and with the help of partner companies, and typically do not impact Steam users. During the Christmas attack, traffic to the Steam store increased 2000% over the average traffic during the Steam Sale.
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.
