What is a Computer Virus?

What is a Computer Virus?

This week I thought it might be a useful exercise to examine some of the constantly changing terms information technology people and others use to name bad software. In vernacular usage, the word “virus” has become a catch-all for any and all kinds of bad software, yet the word virus does have a specific and more restricted definition that sets it apart from other terms.


Strictly speaking, a computer virus is a program that replicates by infecting other computers with copies of itself. In 1981 the very first was “Elk Cloner” that infected Apple computers and this was quickly followed with too many to name that infected Microsoft systems. A worm is basically the same bad program as a virus but a worm simply replicates without a payload. Payload is the term used to describe the damage done by malicious software.


A Trojan is also basically the same bad program as a virus but a Trojan lacks the ability to self-replicate and rather depends on fooling an unsuspecting user into installing it on their system. This also describes a “drive-by-install” which is another bad program that gets installed when the user visits a website and is tricked into clicking on a link that installs unwanted junk software on their computer.


Adware, malware, and spyware, are names given to bad programs responsible for such things as ruining your online experience with excessive advertising or spying on your online activities so that this information can be sold to advertisers. A subset of these bad programs is called a PUP or potentially unwanted program. PUPs fall into a grey area of troublesome software that is not dangerous or malicious, but just rubbish you do not want to have on your computer, tablet, or smart phone.


A keystroke logger is a bad program used to steal your username, passwords, as well as valuable bank account or credit card numbers.


Most pernicious of all is the root kit. Root kits are extremely difficult to detect and forbiddingly impractical to remove from an infected system. Sony Corporation got into trouble, not enough trouble in my opinion, when it created a root kit to destroy a computer’s ability to make copy CDs.


The most recent threat to evolve is called cryptojacking. Cryptocurrencies such as bitcoin are created by “mining” for them using a computer. Mining for coins requires a lot of computing power, and computing power uses a lot of electricity that costs money. Clever computer hackers have figured out ways to sneak mining software onto your computer, smart phone, router, and other internet-connected devices so that they are using your electricity. The bad guys then keep the cryptocoins you mined using your electricity.


And finally, grammarians correctly point out that the word virus is a mass noun with no plural form. Incorrect though it may be, “viruses” is now accepted as part of the tech lexicon.


Charles Miller is a freelance computer consultant, a frequent visitor to San Miguel since 1981 and now practically a full-time resident. He may be contacted at 044 415 101-8528 or email FAQ8 (at) SMAguru.com.