The personal details of 100 million Facebook users have been collected and published online in a downloadable file, meaning they will now be unable to make their publicly available information private.
However, Facebook downplayed the issue, saying that no private data had been compromised.
The information was posted by Ron Bowes, an online security consultant, on the Internet site Pirate Bay.
Bowes used code to scan the 500 million Facebook profiles for information not hidden by privacy settings. The resulting file, which allows people to perform searches of various different types, has been downloaded by several thousand people.
This means that if any of those on the list decide to change their privacy settings on Facebook, Bowes and those who have the file will still be able to access information that was public when it was compiled.