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.
Business Insider obtained a PDF guide that is sold online for just £2.59.
It details how scammers operate fake dating site profiles in order to con men out of money.
The guide isn't available for free, in fact, it was being sold for Bitcoins on a deep web marketplace.
Bitcoin is cryptographic currency favoured by criminals as it allows semi-anonymous online transactions.
It's not just guns and drugs that are up for sale on deep web sites.