Facebook is now issuing warning messages to users if it strongly suspects that an account is being targeted by a hacker working for a nation state. The message (pictured above) also recommends that users turn on "Login Approvals," which means accounts can only be accessed using stronger two-factor authentication.

"These types of attacks tend to be more advanced and dangerous than others," reads a message from Facebook security chief Alex Stamos. "We strongly encourage affected people to take the actions necessary to secure all of their online accounts."

"It's important to understand that this warning is not related to any compromise of Facebook's platform or systems," the post continues, "and that having an account compromised in this manner may indicate that your computer or mobile device has been infected with malware. Ideally, people who see this message should take care to rebuild or replace these systems if possible."

The social network isn't disclosing how exactly it knows when an account is target of unauthorised government surveillance, saying that it has to "protect the integrity" of its methods. It does say, however, that it will only use its new warning "in situations where the evidence strongly supports our conclusion." Google has been offering a similar warning since 2012.

Facebook's latest security scheme follows news earlier this month that the Court of Justice of the European Union struck down the 15-year-old Safe Harbour agreement that allowed the free flow of information between the US and EU. An EU citizen argued that in light of Snowden's revelations about the NSA, the data he provided to Facebook that was transferred from Europe to the US under the Safe Harbour scheme was not safely harboured.

While a victory for the privacy of EU citizens and a blow to the NSA, the ruling will have far-reaching repercussions for companies wanting to transfer data between the EU and the US.