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Virus

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Definitions Edit

A virus is

[a] [s]elf-replicating, malicious code that attaches itself to an application program or other executable system component and leaves no obvious signs of its presence.[1]
a program that "infects" computer files, usually executable programs, by inserting a copy of itself into the file. These copies are usually executed when the "infected" file is loaded into memory, allowing the virus to infect other files. Unlike the computer worm, a virus requires human involvement (usually unwitting) to propagate.[2]
code written with the express intention of replicating itself. A virus attempts to spread from computer to computer by attaching itself to a host program. It may damage hardware, software, or data.[3]

It can be transmitted as an attachment to an e-mail, as a download, or be distributed on a diskette or CD.

Brief history of viruses Edit

Viruses date back to the early days of computers when most viruses were created for fun. Malicious viruses did not surface until the 1980s when the first personal computer (PC) virus, Pakistani Brain (1986), appeared and propagated when the user "booted up" his/her computer from a floppy disc.

Although other types of malicious software appeared in the mid-1980s, the landscape of the late 1980s and early 1990s predominantly consisted of viruses. Until about 1999, most people related viruses to the example of a teenager hacking into the Pentagon's computer systems as seen in the 1983 movie Wargames.

Overview Edit

Viruses are classified as being one of two types: a research virus or an in-the-wild virus.

Viruses typically consist of three parts: a mechanism that allows them to infect other files and reproduce, a trigger that activates delivery of a "payload," and the payload itself, from which the virus often gets its name. The payload is what the virus does to the file or system (besides infecting it). Payloads range from the annoying, such as displaying a message on the screen, to the extremely destructive, such as wiping out all files on the hard drive.

Viruses are often classified by their infection mechanism. The most common type is the file virus, which executes when an infected file is executed (typically, a file with the extension .EXE, .COM, .BAT, or .SYS). The newer macro viruses infect the executable code embedded in Microsoft® Office® programs that allows users to generate macros — sequences of actions initiated by a single keystroke, such as inserting a special character or formatting a paragraph.[4]

How viruses work Edit

A virus requires its host program to run before the virus can become active and generally requires human interaction to activate. The program "infects" computer files, usually executable programs, by inserting a copy of itself into the file. These copies are usually executed when the infected file is loaded into memory, allowing the virus to infect other files.

Viruses may contain a simple message or image that consumes storage space and memory, and degrades the overall performance of a computer, or in the case of a more malicious payload, can destroy files, reformat a hard drive (thereby erasing all of the data on the disk), or cause other damage.

The two major types of viruses are compiled viruses, which are executed by an operating system (OS), and interpreted viruses, which are executed by an application.

References Edit

  1. CNSSI 4009.
  2. Critical Infrastructure Protection: Challenges and Efforts to Secure Control Systems, at 5 n.3.
  3. Privacy and Civil Liberties Policy Development Guide and Implementation Templates, App. E, Glossary.
  4. Practices for Securing Critical Information Assets, at 30.

Source Edit

See also Edit

External resources Edit

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