What is VIRUS??

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.

Properties of VIRUS

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.

How viruses may affect files

Viruses can affect any files; however, usually attack .com, .exe, .sys, .bin, .pif or any data files. Viruses have the capability of infecting any file; however, will generally infect executable files or data files, such as word or excel documents that are opened frequently and allow the virus to try infecting other files more often.

Increase the files size, however this can be hidden. When infecting files, virtues will generally increase the size of the file; however, with more sophisticated viruses these changes can be hidden.

It can delete files as the file is run. Because most files are loaded into memory, once the program is in memory the virus can delete the file used to execute the virus.

It can corrupt files randomly. Some destructive viruses are not designed to destroy random data but instead randomly delete or corrupt files.

It can cause write protect errors when executing .exe files from a write protected disk. Viruses may need to write themselves to files that are executed; because of this, if a diskette is write protected, you may receive a write protection error.

It can convert .exe files to .com files. Viruses may use a separate file to run the program and rename the original file to another extension so the exe is run before the com.

It can reboot the computer when executed. Numerous computer viruses have been designed to cause a computer to reboot, freeze, or perform other tasks not normally exhibited by the computer.

Worm

First developed by John Shoch and Jon Hupp at Xerox PARC in 1978, a worm is a destructive software program containing code capable of gaining access to computers or networks, and once within the computer or network, causes that computer or network harm by deleting, modifying, distributing, or otherwise manipulating the data.
Short for Write Once Read Many, WORM is a type of CD that can be written to and then read from thereafter.

Trojan Horse

A program or utility that falsely appears to be a useful program or utility, such as a screen saver. However, once installed, it performs a function in the background such as allowing other users to have access to your computer or sending information from your computer to other computers.

Malware

Also known as scumware, malware is a type of software program that has been intentionally designed to change a user's settings without his or her permission, delete a competing software program, cause a competing software program to stop working, and/or leave a computer open to attacks.

Spyware

Term used to describe a software program that is intentionally installed on the computer by a user to monitor or spy on what other users of the same computer are doing.

• A term used to describe a software program that has been designed to track a user's activity without the user fully understanding the intentions of the program or not knowing about its installation. Spyware programs are often used to help with tracking users' habits and help with delivering proper advertisements to a user. Spyware is installed onto a user's machine when installing free programs such as free music sharing programs, visiting web pages such as adult oriented web pages, and through other downloads and plug-ins on the Internet.

Adware

Also known as malware, sneakware, or spyware, adware activities and/or habits to help companies is a type of software program thats installed without a users consent or knowledge while another program is being installed on the computer. Much like spyware, an adware program is used to track an individuals Internetadvertise more efficiently.

Adware is commonly installed on a computer with free programs to help support the development of that program. Like spyware, adware can be located and removed from a computer using software utilities available on the Internet. See our spyware page for examples and recommended programs.

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www.webopedia.com/TERM/v/virus.html
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