In an update that raises more questions than it answers, LinkedIn has assured members that the company is working hard to protect their personal data in the wake of a security breach that exposed about 6.5 million hashed LinkedIn passwords.
But the company offered no explanation as to how the passwords had been obtained, how they ended up being posted on a Russian hacker website earlier this week, and what other data might have been compromised.
In a somewhat confusingly worded blog post, LinkedIn director Vicente Silveira said that LinkedIn had "learned" about 6.5 million passwords being posted on a hacker site, but then neither confirmed nor denied that number.
Instead, he merely noted that most of the passwords on the list appeared to remain hashed and hard to decode. "But unfortunately a small subset of the hashed passwords was decoded and published," Silveira said.
This is the first time that LinkedIn has alluded to 6.5 million passwords being compromised. In its first official comment on the incident the company had merely noted that "some" hashed passwords might have been compromised.
Silveira's blog post does not make clear if the hackers who accessed the passwords had also managed to access the associated email logins. Rather, Silveira merely noted that LinkedIn has so far not seen any evidence of LinkedIn email IDs being publicly posted online. "Nor have we received any verified reports of unauthorised access to any member's account as a result of this event," he said.
LinkedIn's first priority in the wake of the incident has been to "lock down and protect" the accounts associated with the decoded passwords, he said. "We've invalidated those passwords and contacted those members with a message that lets them know how to reset their passwords," Silveira said.
"Going forward, as a precautionary measure, we are disabling the passwords of any other members that we believe could potentially be affected," he said.
Silveira again noted that as part of the improved security measures, LinkedIn's current production database for account passwords is salted as well as hashed. Some security experts have faulted LinkedIn for using only the SHA-1 hashing algorithm to protect member passwords.
Though the algorithm provides a degree of security, it is not foolproof. Therefore, many companies also use saltinga process in which a string of random characters are added to a password before it is hashed to make hashes harder to crack.
Chester Wisniewski, senior security advisor at Sophos called Silveira's comments about salting somewhat confusing. "They are saying that their current production database is now salted, which seems to be technically impossible. They either lost the database some time ago and have been adding salts as users log in, which means not all of them are salted, or they have plaintext copies of the passwords, which defeats the purpose of hashing them to begin with," he said.
"The only way to salt an existing hash is to recalculate the hash after a user logs in, or for the users to have all changed their passwords," Wisniewski said.
Silveira's comments about only a few hashed passwords being decoded and published are also puzzling, he said. "Why they believe only a small percentage have been solved is confusing. While only a small percentage have been published, most all of them have been discovered, according to many sources who have been trying to crack them," he said.