January 20, 2011

Virus and Its Properties

A computer virus is a small software program that spreads from one computer to another computer and that interferes with computer operation.Viruses can spread from one system to another system on a network. Computer viruses are most easily spread by attachments in e-mail messages or by instant messaging messages. Therefore, you must never open an e-mail attachment unless you know who sent the message or unless you are expecting the e-mail attachment. Computer viruses also spread by using downloads on the Internet. Computer viruses can be hidden in pirated software or in other files or programs that you may download. A true virus can spread from one computer to another, when its host is taken to the target computer. They are platform independent which means it can affect any operating system depending on its programming function. They can even disable or destroy hardware.


Following is the list of some of the different properties a computer virus and what the particular property is capable of doing. Not all viruses will have every one of these abilities and not all reside in the same location as other:
Your computer can be infected even if files are just copied- Because some viruses are memory resident, as soon as a diskette or program is loaded into memory, the virus then attaches itself into memory and then is capable of infecting any file on the disk you have access to.
They can be Polymorphic- Some viruses have the capability of modifying their code, which means one virus could have various amounts of similar variants. This is also true with e-mail viruses that change the subject or body of the message to help from being detected.
Can be memory or non-memory resident- As mentioned earlier a virus is capable of being either memory resident where the virus first loads into memory and then infects a computer or non-memory resident where the virus code is only executed each time a file is opened.
Can be a stealth virus- Stealth viruses will first attach itself to files on the computer and then attack the computer; this causes the virus to spread more rapidly.
Viruses can carry other viruses- Because viruses are only software programs a virus may also carry other viruses making the virus more lethal and help the primary virus hide or assist the primary virus with infecting a particular section of the computer.
Disguise the system user from their symptoms- Some viruses can hide changes made, such as when a file was last modified making the virus more difficult to detect. They will make the a file replicate or modify, or create a file in the same time when the windows system files are changed or modified by windows.
Can stay on the computer even if the computer is formatted- Some Viruses have the capability of infecting different portions of the computer such as the CMOS battery or master boot record. Finally, if a computer is completely erased and the virus is on a backup disk it can easily re-infect the computer.

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