Define Program Virus

Program Virus — These viruses directly attack the program files of the system with extensions like .EXE, .SYS, .COM, .DLL, etc. Once these programs files are infected with the virus, they start showing unusual behaviour. Since these viruses don't affect the boot sector, the system stays unaffected. When a relevant task related to a program file is performed, it becomes active and starts showing its destructive behaviour. For example, Sunday, Cascade, etc.