Riot Games, the developer of League of Legends, is warning all its 32 million users to change their passwords after hackers breached its western European, Nordic and eastern European database.
Riot confirmed on Saturday that hackers had accessed email addresses, encrypted account passwords, ‘summoner’ names, dates of birth and in some cases first and last name as well as the security question and answer.
It’s unclear exactly how many users' account details were compromised, but the pan-European coverage suggests it would be large.
Riot said no payment or billing information was stolen and that it had fixed the vulnerability that allowed the breach, but warned that its security investigation revealed “more than half” the compromised passwords were simple enough to be easily cracked.
Urging users to pick a unique mixed alphanumeric password of at least eight characters, Riot said it found that 11 passwords were shared by over 10,000 players each.
“A double-digit percentage of individuals had the same password as at least one other person.”
Although the company may have “encrypted” the passwords, Sophos Asia Pacific security consultant, Paul Ducklin points out that it’s unclear whether the passwords were only hashed, salted or repeatedly hashed to fend off “precomputed dictionary attacks”.
A dictionary attack targets weak, easily guessed passwords first by repeatedly attempting to use passwords that are likely to be successful.
“Even with salting and repeated hashing, a dictionary attack is possible, albeit much more slowly than with unsalted, singly-hashed passwords. And hackers try the most obvious passwords first, so that the weakest accounts get cracked soonest,” said Ducklin.
The difference was made clear following LinkedIn’s confirmation that a file containing over 6 million of its users’ hashed but unsalted passwords was floating around a popular cracking forum. It has since begun salting passwords.
It’s not clear exactly how many of The League of Legends users were affected by this password breach, which is the fourth breach confirmed in the past week, including 1.5 million hashed passwords from dating site, eHarmony, and up to 2.5 million from CBS Interactive’s streaming site, LastFM.