Facebook revealed Feb. 15 in a blog post that it was hit by a sophisticated hacker attack last month but that no user data was lost or stolen.
This attack occurred when a handful of the social network's employees visited a mobile developer Website that was compromised, the company reported.
"The compromised Website hosted an exploit which then allowed malware to be installed on these employee laptops," the company said.
"The laptops were fully patched and running up-to-date antivirus software. 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 it then began a significant investigation that is ongoing and added that it has "no evidence that Facebook user data was compromised in this attack."
The Menlo Park, Calif.-based network also said it was not the only site affected in the attack. "It is clear that others were attacked and infiltrated recently as well," the company said.
Facebook said it is working with law enforcement to find out more about the incident.