What is a Computer Virus?

A computer virus is a computer program that has self-replicating capabilities and is designed to corrupt devices or infect computer operations or software. A computer virus may be a disarmingly simple segment of computer code that creates an annoying popup or a full-blown hack attack intended to wreak devastation on a computer's operating system and any devices connected to it. Most commonly, a computer virus targets computing activities or infects computer networks.

A virus scan is an important defense against computer viruses, and many antivirus software solutions that remove infections are available. Reading reviews of antivirus and security software and then choosing the best solution for your needs is important for protecting the security of your computer. Maintaining internet security with security scanning software is also a key defense strategy against infection.

Computer malware comes in many varieties. These include computer viruses that target a computer’s random access memory (RAM), worms that travel through computer networks and Trojan horses. Macro viruses may infect a word-processing application, for example, and then launch a series of attacks. For example, the malware may email the contents of the user’s address book to hackers who will harvest those addresses for sending out volumes of spam.

A boot-sector virus infects your computer through system hardware in the boot sector of the computer's hard disk, or hard drive. These were among the first generation of viruses, and this type of virus can make it difficult or impossible to reboot your computer. Multi-part viruses are also known as hybrid viruses. They may infect both files and system sectors, making it very difficult to cleanse your computer. This type of computer virus commonly leaves a residual source of infection that can re-infect your computer later.

RAM viruses infect a computer's memory and then copy and store files in areas of the file tree where they will later execute each time you open an application. A common warning sign of this type of computer infection is a slowdown in computer operations. These viruses can be mildly annoying or seriously irritating, especially if you encounter a variant that begins to actively erase data on your computer.

Worm viruses replicate themselves onto other computers sharing the same network. They are sometimes used in denial-of-service attacks. For example, worms may infect many computers linked by a network. First, the worm places a command agent on each individual computer, and then hackers execute a command that instructs infected computers to repeatedly attempt to access a particular website many times. So many requests to load a webpage in a short span of time may overload and crash the website's server.

File infectors have been used to crash networks too. An infamous example is the Win32 computer virus. Like living worms, it burrows deep into computer systems and is not dependent upon human actions to replicate.

Flu germs spread most effectively when you don’t know that someone close to you is sick. This is the case with computer viral infections caused by Trojans. These viruses often appear as harmless files that are available to download, but once you run the download, open an infected file or access an infected email attachment, this type of malware sneaks into your system and might turn your computer into a proxy server.

A Trojan virus quickly takes over some of a computer’s processes for nefarious purposes, such as commandeering the computer to use it as part of a botnet along with other commandeered computers. A botnet is a group of computers linked together by hackers to commit large-scale cybercrimes that are untraceable. For example, a botnet may send out volumes of spam with deceitful offers that attempt to trick others and infect more computers, increasing the size and power of the botnet.

Viruses and other threats may also target machines that control mechanical or physical processes. In mid-2010, a computer virus called the Stuxnet worm infected nuclear facilities in Iran and slowed that nation’s progress in enriching uranium-235 – a substance that can be used to make a nuclear weapon. Sometimes malevolent code is developed in a lab for beneficial purposes. Developers may create it to develop protections against infection from the thousands of computer viruses that are in the wild at any given time. A computer virus can even be used to disinfect a computer if it is designed to replicate code that cleanses the infection.

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