The message that flashes across infected computer screens sounds downright scary:

“You have been viewing or distributing child porn … violating article 202 of the Criminal Code of the United States of America,” says one version, allegedly sent by the FBI. A virus victim supplied the message to NBC News.

In each case, the accusation appears on a pop-up screen while the virus simultaneously disables the computer. The message often shows the user’s IP address and city, and sometimes, recent websites visited by the victim. The most alarming version activates the victim’s webcam, takes his or her picture, and displays it on the warning…

The victim is then offered an option: pay a fine within 72 hours, and the charges will be dropped, while the computer will be restored.