Valve finally issued an apology and broke their silence on the details of what they called “Steam’s troubled Christmas”. Last week on Christmas Day, December 25th, Steam users were caught by surprise when they were able to see the account information for other users. The problem persisted for about an hour before Steam was shut down to fix it. Valve issued a small statement regarding the incident shortly after to the media.
“As a result of a configuration change earlier today, a caching issue allowed some users to randomly see pages generated for other users for a period of less than an hour. This issue has since been resolved. We believe no unauthorized actions were allowed on accounts beyond the viewing of cached page information and no additional action is required by users.”
Questions still lingered from users who were unsure whether or not their information was compromised but Valve had been very hush about the issue until today where they explained exactly what had happened.
The statement explains that the problem resulted from a combination of Denial of Service attacks and the amount of increased traffic to the Steam store that day. DoS attacks are common and usually do not affect users however the attempts to thwart these attacks on that day lead to a caching error which resulted in users being able to see other people’s account information.
Valve assures those who were affected by the error that outside of being able to view the information, no unauthorized actions could have been made. Those affected will be contacted by Valve after they’ve been identified and no further action is required. Those who were not browsing the Steam store during the time frame in which the incident happened do not need to worry about their account information being viewed by others.
The full statement:
What happened
On December 25th, a configuration error resulted in some users seeing Steam Store pages generated for other users. Between 11:50 PST and 13:20 PST store page requests for about 34k users, which contained sensitive personal information, may have been returned and seen by other users.
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. 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 working with our web caching partner to identify users whose information was served to other users, and will be contacting those affected once they have been identified. As no unauthorized actions were allowed on accounts beyond the viewing of cached page information, no additional action is required by users.
How it happened
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.