A portion of the North American user base of "League of Legends" (LoL) had its account information compromised by hackers, according to Riot Games, the company developing the popular online multiplayer game. Passwords and credit card numbers stored in encrypted form were accessed, as well as other details.
"What we know: usernames, email addresses, salted password hashes, and some first and last names were accessed," Riot Games founders Marc Merrill and Brandon Beck said in a blog post. "This means that the password files are unreadable, but players with easily guessable passwords are vulnerable to account theft."
Furthermore, the company is also investigating the unauthorized access of 120,000 transaction records dating from 2011 that contained credit card numbers in the form of salted hashes.
Hashing is a form of one-way encryption where plaintext data, be it a password, a credit card number or something else is passed through an algorithm to generate a unique cryptographic representation of it, a random-looking string of characters referred to as a hash.
A hash is not meant to be decrypted to recover the original plaintext information, but can be used to validate that information if inputted at a later time. For security reasons modern websites store hashes in their databases instead of passwords.
When users input their passwords to authenticate, those passwords are passed through the hashing function again and the resulting hashes are compared with the ones that were stored in the database when those passwords were originally created. A matching hash indicates that the user provided the correct password.
Even though hashing is a one-way street, some hashing algorithms are vulnerable to brute force attacks, testing plaintext combinations to find the one matching a targeted hash. In order to make such attacks harder, it is common to append a random string to each plaintext before hashing it. This process is known as salting.
The likelihood of the LoL hashes being cracked by those who copied them, is highly dependant on what hashing algorithm was being used by Riot Games on its systems and how salting was implemented.
Riot Games did not disclose such details in its announcement and the company didn't immediately respond to a request for comment seeking more information.
The payment system that generated the 120,000 transaction records now accessed by unauthorized individuals hasn't been used since July 2011 and similar records haven't been collected by any other Riot systems since then, Merrill and Beck said.
"We are taking appropriate action to notify and safeguard affected players," the two Riot founders said. "We will be contacting these players via the email addresses currently associated with their accounts to alert them. Our investigation is ongoing and we will take all necessary steps to protect players."
As a preventive measure, all North American users will be forced to change their account passwords to stronger ones, Merrill and Beck said in the blog post.
However, this mandatory password reset decision seems to have been extended to also include, at the very least, players on the European West (EUW) and EU Nordic & East (EUNE) servers, with password reset notices being posted on the regional websites corresponding to those servers.
Riot Operates separate LoL gameplay servers and websites in several regions, including North America, Latin America, Western Europe, Northern and Eastern Europe, Russia, Turkey and Oceania.
European LoL players have been affected by an incident that resulted in hackers accessing their account information, including password hashes, before, in June 2012. The company did not enforce mandatory password resets for all users at the time, but advised them to change their passwords to something stronger, noting that more than half of the affected password hashes corresponded to simple passwords and were at risk of easy cracking.
Following this new incident, the company plans to implement additional account security features, including email-based validation of changes to password and contact information, and two-factor authentication, Merrill and Beck said.
Last October, Riot said that League of Legends had around 70 million registered users, 12 million of whom were active on a daily basis. In March 2013, the company said that the game regularly exceeds five million peak concurrent players globally.