Victims are lured to a drive-by download Web site where the ransomware is surreptitiously installed on the user's computer. Once infected, the computer freezes and a screen is displayed warning the user they have violated federal law, the FBI said in a statement on its Web site.
The message states the user's Internet provider address was identified by the Computer Crime and Intellectual Property Section as having visited sites that feature child pornography and other illegal content.
To unlock the computer, the user is instructed to pay a $100 fine to the U.S. Justice Department using prepaid money card services. The geographic location of the user's IP address determines what payment services are offered.
The malware remains on the computer and can be used to commit online banking and credit card fraud, the FBI said.
The FBI said anyone who encounters the ransomware should not follow payment instructions. The agency suggests victims contact their banking institutions and file a complaint at www.ic3.gov.