It's called scareware, and it's become a big problem for Internet users. According to the FBI, one of the groups infected 960,000 computers, costing users US$72 million. A second group made about $2 million by placing fake ads on the Minneapolis Star Tribune's website.

Two people were arrested Tuesday in Rezekne, Latvia, in connection with that second group. They are Peteris Sahurovs, 22, and Marina Maslobojeva, 23. Both face wire fraud and computer fraud charges in the U.S.

Scareware works by displaying a pop-up message on the victim's screen with a fake but scary-looking virus warning. The warning pesters the victim until they pay money to the criminals -- sometimes more than $100 -- for what they think will be antivirus software to fix the problem. Paying the money usually makes the warnings go away, but handing over a credit card number to an unknown party can lead to credit card fraud and other problems.

The FBI, along with law enforcement agencies in the U.K., the Netherlands, Latvia, Germany, France, Lithuania and Sweden, seized 22 computers in the U.S. and 25 more overseas. They also worked with Latvian police to seize bank accounts belonging to the alleged scammers.

The IDG News Service