It's significantly larger than the hack of extramarital affairs dating website Ashley Madison back in 2015, which saw nearly 40 million user accounts leaked to the world.
If a company gets breached or uses shoddy security practices, there's little users can do about it.
But you can mitigate the fallout by using a different, secure password for every site or service you have an account with, storing them with a password manager app if necessary.
Friend Finder Networks, the company behind adult dating site Adult Friend Finder has been hit with a massive hack — exposing more than 400 million user accounts.
The news comes via Leaked Source, a site that monitors data breaches, which has obtained a copy of the stolen user accounts.
If you've used a dating site or app like Ok Cupid or Tinder, you'll have noticed the hundreds of fake profiles that exist on the sites, seemingly designed to make you hand over your profile to scammers.
Dating sites are, thankfully, getting better at spotting who is using their service to send thousands of spam messages.
The 412 million accounts go back 20 years, it says, and the lion's share comes from Adult Friend Finder — almost 340 million.
Another 63 million come from adult webcam site Cams.com, 7 million come from adult magazine Penthouse.com, and over a million apiece from and i
Friend Finder Networks did not immediately respond to Business Insider's request for comment.
But it told ZDNet, which also verified a sample of the data, that "over the past several weeks, Friend Finder has received a number of reports regarding potential security vulnerabilities from a variety of sources.
Some premium dating sites eventually need new male and female members, even free members, in order to expand their member base and get some fresh faces.