The private details of over 4m users of AdultFriendFinder have been hacked and posted on the deep web.
A Channel 4 News investigation into the cyber underworld found that the site, which claims over 63m members, had sensitive data stolen by a hacker.
The hacked information includes the sexual preferences of users, their sexual orientation and whether they were looking for extramarital affairs.
Personal data like email addresses, usernames, DOBs, post codes and user ISPs were also hacked.
The news agency discovered that a hacker named ROR[RG] posted the stolen AdultFriendFinder details on a secret forum on the deep web.
The details that were being traded included that of those who has supposedly deleted their accounts.
After the data was leaked, hackers on the forum said they were planning on sending spam emails to victims containing viruses.
Crime experts told Channel 4 that after this, the hackers were likely to identify potential targets for blackmail.
AdultFriendFinder describes itself as a “thriving sex community” with 63m worldwide members, and over 7m from the UK.
The company told Channel 4: “FriendFinder Networks Inc… understands and fully appreciates the seriousness of the issue.
“We have already begun working closely with law enforcement and have launched a comprehensive investigation with the help of leading third-party forensics expert.
“We pledge to take the appropriate steps needed to protect our customers if they are affected.”
In 2013, FriendFinder Networks filed for bankruptcy after a loss of around $50m in 2012.