People can now enter their own phone number on the website and check if it appears in the last data leak from Facebook. Details of more than 530 million people have leaked into an online database, mostly consisting of mobile phone numbers.
They can use the internet tool Have I Been Pwned to check if their numbers or emails have been compromised.
Facebook says that the data are from the "old" data security violation from 2019, but the privacy controllers have already launched an investigation. Facebook also says it "found and repaired" the data security breach more than a year and a half ago.
But that information is now being offered for free on a hacker forum, making it widely available.
This database covers 533 million people from 106 countries, according to researchers analyzing the data. That applies to 11 million Facebook users in the UK, 30 million Americans and 7 million Australians.
Not all user data is available, but 500 million phone numbers have been leaked, as opposed to "only a few million email addresses," wrote Troy Hunt, a security expert who runs the HaveIBeenPwned site.
Visitors to the site can now enter their own mobile phone number in the search window, and the page will confirm whether it appears in the leaked database.
"I wanted to make sure Have I Been Pwned could answer that question for everyone, not just a fraction of the people," says Hunt.
It has been suggested that even the mobile phone number of Facebook owner Mark Zuckerberg leaked into the database. Is the fact that Mark Zuckerberg's phone number leaked just a good joke to show that he is "innocent", or is it a real theft of his number as well.