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Program Virus
A Program Virus infects programs installed on a computer. Program files usually
have extensions such as .exe, .com, .sys, .bat, .dll, .bin, and .pif. When the
infected program is executed, the virus becomes active in the memory, making
copies of itself and infecting all files accessed by the infected program. Sunday,
Cascade, Acid Rain, and Amoeba.A are some examples of program viruses.

Macro Virus

A Macro is a set of instructions used to automate tasks that are
performed more often, such as creating or deleting files, or modifying
the contents of existing files. A Macro Virus infects macros written
for software such as Microsoft Word, Excel, and PowerPoint. Macro

viruses infect documents that use the infected macros and overwrite or completely destroy the data in
the documents. Melissa, Relax, Concept, and Nuclear are some examples of macro viruses.
Multipartite Virus
A Multipartite Virus infects a computer and spreads in multiple ways. It attacks both the boot sector and
the program files. Ghostball, Tequila, and Invader are some examples of multipartite viruses.

Polymorphic Virus
A Polymorphic Virus is a virus designed to avoid detection by antivirus software.
It changes its program code every time it replicates and infects a new file.
Marburg, Tuareg, and Satan Bug are some examples of polymorphic viruses.

Stealth Virus
A Stealth Virus is capable of hiding itself inside data files. It is able to
deliberately avoid detection by antivirus software. Frodo, Joshi, and
Whale are some examples of stealth viruses.

Knowledge Discovery Subject Enrichment
A rootkit is a malicious software designed to give unauthorised access to a
computer. Rootkits can conceal their presence within an infected system.
Hackers use rootkits to remotely access your computer, manipulate it, and
steal data. Rootkits appear to be legitimate, but they make your computer lie
to you, the antivirus, and the security software. Rootkits hide other malware
within your device and make it harder to remove them.

Worm
A Worm is malware that stays inside the memory of computer and
replicates itself automatically to other computers through computer
networks without any human interaction. Unlike a virus, a worm usually
does not cause damage to programs or data in a computer but consumes
too much system memory or network bandwidth, causing servers
and individual computers to stop responding. Morris, Mydoom, and I
LOVEYOU are some examples of computer worms.

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