<P> A viable computer virus must contain a search routine, which locates new files or new disks which are worthwhile targets for infection . Secondly, every computer virus must contain a routine to copy itself into the program which the search routine locates . The three main virus parts are: </P> <P> Infection mechanism (also called' infection vector'), is how the virus spreads or propagates . A virus typically has a search routine, which locates new files or new disks for infection . </P> <P> The trigger, which is also known as logic bomb, is the compiled version that could be activated any time an executable file with the virus is run that determines the event or condition for the malicious "payload" to be activated or delivered such as a particular date, a particular time, particular presence of another program, capacity of the disk exceeding some limit, or a double - click that opens a particular file . </P> <P> The "payload" is the actual body or data that perform the actual malicious purpose of the virus . Payload activity might be noticeable (e.g., because it causes the system to slow down or "freeze"), as most of the time the "payload" itself is the harmful activity, or some times non-destructive but distributive, which is called Virus hoax . </P>

What is virus and different types of virus