Type
(MBR, OSboot, COM/EXE, exe, com)
A type of a virus is determined by the different kinds of targets
the virus infects.
For example possible targets are *.com files, *.exe files, boot
sectors, master boot records.
Multipartite
Some viruses infect both executables, and master boot records. These
are called Multipartite viruses.
Overwriting Virus
Overwriting viruses replace the code of the victim with the virus
code, thus destroying the victim irreparably.
Companion Virus
Companion type viruses create a same named executable with a .com
extension, in order to utilize the feature of DOS which dictates
that if there are same named executables in the same directory,
the one with the .com extension is executed first.
(NON-) Resident Virus
A resident virus stays in memory after execution. Resident viruses
are able to thus spread without the user executing them once they
are in memory. Whereas non-resident viruses are able to
spread only when the user executes an infected program.
Stealth Virus
A stealth virus hides its presence so the user can not detect the
decrease of memory or the increase in infected files sizes.
