Blackshades is a malicious trojan horse used by hackers to control infected computers remotely. The malware targets computers using operating systems based on Microsoft Windows. According to US officials, over 500,000 computer systems have been infected worldwide with the software. In 2014, the United States Federal Bureau of Investigation (FBI) arrested hundreds of people who had Blackshade in their computer. Before the FBI crackdown, Blackshades was sold for US$40 on Hack Forums, and reportedly generated US$350,000 in sales.