Facebook announced that it had been hit by a "sophisticated attack" on its systems on February 15th, while reassuring users that it appeared none of their data had been compromised.
The attack was developed last month when Facebook employees visited a compromised website, which installed sophisticated malware programs on their laptops, according to Facebook's release on the matter.
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Facebook said it had alerted law enforcement and had launched an "ongoing investigation" into the hacks.
The release added that Facebook wasn't the only website to be hit by the attack, and noted that "we immediately took steps to start sharing details about the infiltration with the other companies and entities that were affected."
Hackers are encouraged to break through Facebook's security walls and report issues, in exchange for a sizable bounty, via the Bug Bounty Program.
The social network's last brush with bugs came earlier in the month, when a redirection bug made popular websites using Facebook's social networking features temporarily invisible for a brief period.