Data affecting more than 500 million Facebook users that was originally leaked in 2019, including email addresses and phone numbers, has been posted on an online hackers forum, according to media reports and a cybercrime expert.

"All 533,000,000 Facebook records were just leaked for free," Alon Gal, chief technology officer at the Hudson Rock cybercrime intelligence firm, said Saturday on Twitter. He denounced what he called the "absolute negligence" of Facebook.

Some of the data appeared to be current, according to a report in Business Insider which AFP was unable to confirm independently. It said some of the leaked phone numbers still belong to the owners of Facebook accounts.

"This means that if you have a Facebook account, it is extremely likely the phone number used for the account was leaked," Gal said. 

But Facebook said the reports were old news.

"This is old data that was previously reported on in 2019," a company spokesperson told AFP. "We found and fixed this issue in August 2019."

Close to 32 million American accounts and 20 million French accounts were among those affected, Gal tweeted in January, when the person holding the data was trying to sell it. 

The data include phone numbers, complete names, birth dates and, for some accounts, email addresses and relationship status.

"Bad actors will certainly use the information for social engineering, scamming, hacking and marketing," Gal said on Twitter.

This is not the first time leaks or use of data from the world's largest social network – with nearly 2 billion users – has embroiled Facebook in controversy.

In 2016, a scandal around Cambridge Analytica, a British consulting firm that used the personal data of millions of Facebook users to target political ads, cast a shadow over the social network and its handling of private information.