FACEBOOK has solved the mystery of who was behind this year’s major hack attack, a new report claims.

The company has been silent about who conducted the cyber-attack since publicly revealing the breach in late September.

Facebook initially admitted that it had given hackers complete access to 50million accounts – but later trimmed the figure to 30million.

These hackers were able to “use the account as if they were the account holder”, according to one top official.

But Facebook has been closely guarding the identity of the attackers during its investigation.

Now the Wall Street Journal reports that it was “spammers” who logged into tens of millions of accounts illegally.

Security researchers at Facebook HQ may have discovered who was behind the attack

The report notes that the “preliminary findings” suggest that the hackers weren’t associated with any nation state.

This quells fears that powerful cyber-giants like Russia, China or North Korea may have been involved in the attack.

Instead, the WSJ writes that the attackers were “spammers looking to make money through deceptive advertising”.

The report is based on several sources “familiar with the company’s internal investigation”, but weren’t named.

Facebook declined to comment specifically on these claims when asked by The Sun.

However, a spokesperson directed us to an earlier statement from Facebook’s Guy Rosen, who said: “We are cooperating with the FBI on this matter.

“The FBI is actively investigating and have asked us not to discuss who may be behind this attack.”

According to the WSJ, internal researchers believe the attackers are a group of “Facebook and Instagram spammers”.

These so-called spammers reportedly present themselves as a digital marketing company who make money with dodgy ads.

The breach – described as a security “disaster” by experts – was possible thanks to several bugs in Facebook’s systems, which were exploited by hackers.

It meant that attackers were able to log in as absolutely anyone – and access their profiles, photos, friend lists, and even private messages.

Facebook logged 90million users out as a safety precaution, but the bugs had been live in the website’s code since June 2017.

The Sun recently revealed how Facebook faces a maximum fine of just £1.25billion, which is less than 3% of CEO Mark Zuckerberg’s fortune.

And we also told how Facebook could be forced to pay affected Brits £6,000 because of the attack.

Do you trust Facebook? Let us know in the comments!