A computer virus is a type of malicious software capable of self-replication. A virus needs human intervention to be run and it can copy itself into other computer programs, data files, or certain sections of your computer, such as the boot sector of the hard drive. Once this happens, these elements will become infected. Computer viruses are designed to harm computers and information systems and can spread through the Internet, through malicious downloads, infected email attachments, malicious programs, files or documents. Viruses can steal data, destroy information, log keystrokes and more.