Facebook has started to notify users when it suspects they've been targeted by government-sponsored hackers, rather by than run-of-the-mill cybercriminals.
"Starting today, we will notify you if we believe your account has been targeted or compromised by an attacker suspected of working on behalf of a nation-state," Facebook's chief security officer Alex Stamos said in a Notes post on the weekend.
The notification users will see when Facebook detects that they are probably being targeted by a state-sponsored hacker advises them to turn on its two-factor authentication feature, Login Approvals, which requires the user give Facebook their phone number.
Facebook sends users a login code to the person's phone the next time it detects an account has been accessed from a new device or browser.
"We decided to show this additional warning if we have a strong suspicion that an attack could be government-sponsored. We do this because these types of attacks tend to be more advanced and dangerous than others, and we strongly encourage affected people to take the actions necessary to secure all of their online accounts," Stamos said.
Facebook won't be revealing how it tells when a state-sponsored hacker is targeting a particular user, although there are numerous pieces of known malware that are suspected to have been created by government-backed hackers, such as the Stuxnet, thought to have been built by the US, Duqu, DarkSeoul, supposedly from North Korea, China's ShadyRAT and Russia's The Dukes malware.
"To protect the integrity of our methods and processes, we often won't be able to explain how we attribute certain attacks to suspected attackers. That said, we plan to use this warning only in situations where the evidence strongly supports our conclusion," Stamos said.
The new hacker alert notifications join Facebook's other security efforts, such as its security check-up tool, and teaming up with several antivirus vendors to offer online malware scanning and clean-up tools.
Facebook earlier this year said it helped clean up two million infected PCs after using a "combination of signals" to find the infections. While helpful at cleaning up malware, some users have objected to being locked out of their accounts until they download anti-malware from Facebook's partners.