Hackers broke into the network of popular document sharing service Scribd earlier this week and may have compromised “less than 1 percent” of its users’ passwords, according to the company.
Scribd quietly announced the breach on Wednesday in a support page post, stating that its operations team discovered and blocked suspicious activity on its network earlier this week.
“We believe we detected it almost immediately,” Jared Friedman, Scribd co-founder and chief technology officer told CSO.com.au by email.
Scribd salts and hashes its passwords, which should, depending on the algorithm, provide some protection against attempts to crack accessed passwords, however a “small percentage” of passwords stored using an outdated algorithm are believed to have been compromised.
Friedman said Scribd had notified “less than 1 million” users by email whose passwords it believed were compromised.
Content, payment and sales-related data were not accessed or compromised, according to Scribd, while usernames, emails and encrypted passwords were accessed. Less than one percent of passwords were potentially compromised, it said. Scfribd has also set up a password check page for users to find out if they are affected.
The breach was first reported via a submission on Hacker News, where a Scribd software engineer Dmyrto Shteflyuk explained how it defined “compromised” passwords.
“To clarify: no accounts were accessed by the hackers, but small amount of account records have had passwords encrypted with outdated algorithm (basically SHA1 + salt), so we preemptively reset their passwords and sent out emails to all affected users. This is how we define "compromised" - people which had their passwords hash with old algorithm, which is relatively easy to crack,” wrote Shteflyuk (kpumuk).
Norwegian security and password expert Per Thorsheim said in a Tweet that Scribd’s use of scrypt to store passwords was “fantastic news”.
“This is modern hard to crack password hashing algorithm. We do have database access logs, so it was pretty straightforward to identify which users were affected,” wrote Shteflyuk.
Scribd noted that a number of “high-profile websites” had been hit in the past year with “similar attacks”.
According to Friedman, the breach occurred after cryptographic keys that staff use to access Scribd’s systems were compromised.
“The breach occurred when security keys issued to an employee were compromised. We have taken measures to prevent a similar situation from re-occurring in the future,” he said.
Scribd said it was in the process of alerting relevant authorities to the matter and will be co-operating with their investigation.