PREVIOUS

Virus ABCs

One of the biggest fears among new computer users is being infected by a computer virus or programs designed to destroy their personal data. Viruses are malicious software programs that have been designed by other computer users to cause destruction and havoc on a computer and spread themselves to other computers where they can repeat the process.

Once the virus is made, it is often distributed through shareware, pirated software, e-mail, P2P programs, or other programs where users share data

A computer virus is a software program that was first written Rich Skrenta in 1982 who was a 15-year old high school student. Known as The Elk Cloner this virus spread to other computers by monitoring the floppy drive and copying itself to any floppy diskette that was inserted into the computer. Once a floppy diskette became infected it would infect all other computers that disk was inserted into, each computer that was infected would then infect every floppy diskettes inserted into it. A computer that was infected would also display a short poem on every 50th boot.

Computer users can help protect themselves against computer viruses, malware, and other computer security threats by installing an antivirus protection program.

Also see our virus question and answer section for other common questions about computer viruses.

How computer viruses are contracted

In the past the majority of computer viruses were contracted from users sharing data using floppy diskettes. However, with the increased popularity of the Internet most computer viruses are contracted today through e-mail and by downloading software over the Internet or P2P sharing.

Virus properties

Below is a listing of some of the different properties a computer virus is capable of having and what the particular property is capable of doing. Not all viruses will have these abilities, however there are some viruses that will.


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 computer you have access to.


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.


Can make the system never show outward signs. Some viruses can hide changes made, such as when a file was last modified making the virus more difficult to detect.


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.

NEXT