The largest social network in the world is the latest high-profile site to say it's been hacked this year - but it says no ndta about its more than a billion users was compromised.

Facebook described the "sophisticated attack" in a blog post on Friday, saying it took place in January when a small number of employees visited a compromised website that installed malware on their machines.

Twitter announced a similar intrusion earlier this month, and major news organizations including The New York Times, Wall Street Journal and Washington Post have also admitted to being hacked.