Definitions
Here are the definitions from F-Prot's Virus.TXT, one of the most official and
accurate definitions around.
What is a computer virus ?
Well, the best definition we have been able to come up with is the
following:
- A virus is a program that is able to replicate, that is create (possibly modified) copies of itself.
- The replication is intentional, not just a side-effect.
- At least some of replicants in turn are also viruses by the same definition.
- A virus has to attach itself to a "host", in the sense that execution of the host implies execution of the virus.
#1 distinguishes viruses from non-replicating malware, such as ANSI bombs.
#2 distinguishes between viruses and programs such as DISKCOPY.COM
that can replicate.
#3 is needed to exclude certain "intended viruses", that attempt to
replicate, but fail - they simply do not qualify as "real" viruses.
#4 is necessary to distinguish between viruses and worms, which do not
require a host.
- Replication: Yes
- Replication is intentional: Yes
- Replicants are also viruses: Yes
- Attaches to a host: Yes. This virus attaches itself to the host WSOCK32.DLL.
In the HAPPY99.EXE form, it is a worm, since it does not attach to a host. So
calling it a virus and calling it a worm are both correct.