: Computer virus is a malicious program. Computer viruses enter the computer's memory from an external source and spread secretly in the memory, valuable programs , in addition to wasting data, often paralyzing the computer. A virus is a program that infects itself by setting itself up (ie, its "executable" part) as a destroyer with other programs and ensuring the spread of its destruction over time. These infected programs, in turn, transmit the virus to other non-infected programs. As a result, the first program transmits the virus to other good programs.