Facebook said on Friday that it been the target of a series of attacks by an unidentified hacker group, but it had found no evidence that user data was compromised.
"Last month, Facebook security discovered that our systems had been targeted in a sophisticated attack," the company said in a blog post. "The attack occurred when a handful of employees visited a mobile developer website that was compromised."
The social network, which says it has more than one billion active users worldwide, added: "Facebook was not alone in this attack. It is clear that others were attacked and infiltrated recently as well."