There is no specific definition of a "computer virus class 7" in the search results. However, based on the information available, a computer virus is a type of malicious software that infects computers and corrupts their data and software. It is a small piece of software that piggybacks on real programs and can attach itself to another program or file, make its own copies, and harm the performance of a computer system. Computer viruses can be spread via email, infected email attachments, compromised application stores, and infected code repositories. There are several types of computer viruses, including resident viruses, non-resident viruses, boot sector viruses, and macro viruses.