Anyone with an email account connected to the Internet has received them — seemingly endless variations on weirdly phrased emails pretending to be from semi-famous people, offering millions of dollars if you’ll help do something that seems slightly shady. They often originate in Nigeria, and they’re a plague upon the web. And they actually do trick some people into giving away their money.

Want to know how a Nigerian email scammer thinks?

Scam-Detective: What kind of scams were you involved with?

John: Mainly advance fee fraud where we would tell people that someone has died and left millions in a bank or safety deposit box and that we needed help to get it out of the country. That is the most successful type of scam, but I also did Phishing to try and get user names and passwords for peoples online bank accounts.

Scam-Detective: How did you find victims for your scams?

John: First you need to understand how the gangs work. At the bottom are the “foot soldiers”, kids who spend all of their time online to find email addresses and send out the first emails to get people interested. When they receive a reply, the victim is passed up the chain, to someone who has better English to get copies of ID from them like copies of their passport and driving licenses and build up trust. Then when they are ready to ask for money, they are passed further up again to someone who will pretend to be a barrister or shipping agent who will tell the victim that they need to pay charges or even a bribe to get the big cash amount out of the country. When they pay up, the gang master will collect the money from the Western Union office, using fake ID that they have taken from other scam victims.

Scam-Detective: But where do the “foot soldiers” find the email addresses?

John: Lots of people sign guestbooks online and leave their email addresses all over the internet on forums and websites. We would just visit the guestbooks, forums and websites and harvest the email addresses. Some gangs have software that collects these emails automatically, so it cuts down on the work.

Scam-Detective: What percentage of emails would get a response?

John: Maybe 9 or 10 out of every thousand emails. Then maybe 1 out of every 20 replies would lead to us getting money out of the victim in the end.

Scam-Detective: And how much money would you expect to get from a victim?

John: On average, about $7,500 (£4,600) but the most I know about was $25,000 (£15,400). This would be taken in smaller amounts, starting with a couple of hundred, then there would be more “problems” with the transaction, which would mean that we needed more money to release the big payout. People would keep paying more because they were very small amounts compared to the big payout that they believed they would get in the end.