ABSTRACT: Computer viruses poses problems for users of personal computers.These viruses have been from mid 1980s.A computer virus is a special kind of computer program which spreads across disks by making copies of itself.In order to infect a computer the virus should have the chance to execute its code.As long as the computer is infected with virus can copy itself to other files or disks that are accessed. DEFINITION:A computer virus is a software program with a ability to make copies of itself ,which attacks itself to other applications or files. Types of computer Virus. § There are three types of computer virus v Boot virus v Program virus v Micro virus 1. Boot virus: Boot viruses infects the boot records of hard disk and floppy disks. Generally these are considered more dangerous than program viruses. 2. Program Virus: These viruses infect program files, which have extensions such as .COM,.EXE