FBI, Facebook track hackers FACEBOOK, the operator of the largest social network with more than 1 billion members, is working with the FBI to investigate a malware attack. Facebook said it was subjected to a "sophisticated attack" by hackers last month, without saying where the attack originated. Investigators have not found any evidence that user data was compromised, Facebook said on its website. Facebook, which stores information on users, often grapples with attempted breaches. It has a team dedicated to detecting and responding to attack attempts, pays bounties to outside programmers who help identify malfeasance and said it successfully prevented attacks the "vast majority of the time." "As soon as we discovered the presence of the malware, we remediated all infected machines, informed law enforcement, and began a significant investigation that continues to this day," Facebook said on Friday. The malware infected laptops used by Facebook employees when they visited a mobile developer's website, the company said. The attack affected other companies, Facebook said, without identifying them. It is collaborating on the attack through an informal working group. "We are working continuously and closely with our own internal engineering teams, with security teams at other companies, and with law enforcement authorities to learn everything we can about the attack, and how to prevent similar incidents," Facebook said. Twitter said on February 2 it was subjected to hacking attempts, and attackers might have obtained access to information on about 250,000 people. It said the perpetrators were "extremely sophisticated."