Kai Ryssdal: The Department of Justice is suing AT&T. The government says the company wrongfully collected millions of dollars from a federal program that helps the hearing impaired make phone calls. AT&T says it didn’t know that foreign scammers were abusing the service, most of them from Nigeria.

Any time the feds get stiffed out of millions of dollars, it’s a problem. But what is it with all these fakes coming from Nigeria anyway?

Marketplace’s Eve Troeh got the assignment this morning.

Eve Troeh: Look in your spam folder right now, and you’ll likely find a message from a Nigerian prince. He needs your help to wire millions of dollars, and says you’ll be handsomely rewarded. But really, you’ll just have your identity stolen.

Tech writer Chris Null says Nigerian scams exploded in the 1990s, when the country’s oil industry busted and Internet cafes were taking off.

Chris Null: There were a lot of people with some communication skills, that knew English, that knew some technology and they were suddenly unemployed, and they turned to crime.

He says Nigerians have been doing this for decades now because it actually works. The FBI says the scams lure millions of dollars every year.

Null: I’m sure it’s been passed on from father to son, and it’s proven successful, so why stop?

The AT&T case shows how Nigerian scams have evolved. Scammers took stolen credit card numbers and made big orders from U.S. companies over the phone. To mask their identity, they used something called the IP Relay system. It lets disabled people type messages online and send them as phone calls. The operator reads the message to the recipient, and the government pays back the phone company for this service. But only for domestic users. The Department of Justice says AT&T knew most of these requests came from Nigeria, and took reimbursement anyway.

Roger Kay at Endpoint Technologies says that’ll be hard to prove.

Roger Kay: I think it’s a blind eye is the way you describe it, and the question is to what degree shouldn’t you have been blind.

AT&T says the scammers abused the system unbeknownst to the company, just as they would with the post office or an email provider.

I’m Eve Troeh for Marketplace.