LinkedIn Corp is working with the FBI as the social network for job seekers and professionals investigates the theft of 6.4 million member passwords, the company said on Thursday.
The company does not know of any accounts that were taken over as a result of the security violations, according to LinkedIn spokesman Hani Durzy.
A spokeswoman with the FBI declined to comment.
LinkedIn is still in the early stages of the investigation. Durzy said it was not yet determined whether the email addresses that corresponded to the hacked passwords were also stolen.
On Wednesday, LinkedIn confirmed that millions of passwords were stolen. The company sent affected members emails explaining how to change their passwords.
Several security experts said that LinkedIn's stolen passwords had not been adequately secured and that the company did not employ best practices utilized by the world's largest websites.
When asked to comment on that criticism, Durzy said that LinkedIn had already boosted the security of its database. "We place the highest value on the security of our members' data," he said.
The attack on LinkedIn is the latest in a series of security breaches that could affect sensitive consumer data. The online dating service eHarmony warned on Wednesday that some of its user passwords had been breached after security experts discovered scrambled files with passwords for millions of online accounts.
LinkedIn caters to companies seeking employees and people scouting for jobs. It has more than 161 million members worldwide and makes money by selling marketing services and premium subscriptions.
Shares of LinkedIn closed up 1.1 percent at $94.13 on Thursday on the New York Stock Exchange.
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