Understanding Anti-Virus Scanners Terminology

On a regular basis we are asked by customers to explain what some of the more common terms used by several Anti-Virus applications mean. Here is a list of a few of the more common terms:

Malware: This term is used to describe programs or files which are copied / installed onto a computer with the sole purpose of causing harm (ie: viruses, spyware, trojans, worms, hijackers, dialers ..)  Some of these are listed below:

Adware This is a type of program which produces / generates popup pages / advertisements normally in your web browser. 

Backdoor This is a program installed on a computer which allows other people to remotely connect to your computer and run various commands / programs without a users permission.  In some cases hackers can also fully take full control your computer and access everything stored on it. (Note: some Anti-Virus scanners may pick up legitimate programs as backdoors – ie: “teamviewer” or “logmein” at times have been logged as a backdoor as these types of program, even though legitimate, allow remote users to control a persons computer without actually been present at it.)

Dialer – This type of infection dials premium rate telehone numbers without the user realising this is actually taking place.

Hijackers – This is code which tries to take control of certain Web Browser / Internet functions – ie: It may change your home page or set up links to re-direct you to where it wants you to go while surfing the web.  Hijackers have also been known to replace search engine results with their own information.

Spyware – This type of infection monitors activity on a computer and normally forwards details of that activity onto a remote system somewhere – instances of spyware can included “keyloggers” (programs which record every key stroke made on a computer), and have even been know to access things like web cameras.

Trojan – This is normally a type of program which appears normal / innocent (like a free Anti-Virus Scanner or a free system scanner) but has actually been designed to open a backdoor into your system or cause some other type of malicious activity.

Virus – This is an infection which has the ability once on your system to replicate itself many times and infect other files on your computer, thus making them dangerous also.  Viruses can move about systems very quickly and can even be transfered to memory sticks and across networks.  Once a virus is on your system its intention could be to do one of several things including: erasing data from you computers hard drive, messing up the Windows registry, displaying annoying messages, blocking normal Windows process from running as they should …  the list goes on and on. 

Worm – This type of program will generally hide on a system and once activated can replicate and sends itself to other computers using email contact lists or other Web Browser Security Flaws.

Even though this list is not extensive, I hope it helps those who feel understanding the terminology used within the IT security field a little daunting.


  • Comments by David Morgan
  • Many thanks Dominic for your speedy response to our computer problems. You arrived promptly and solved the problems very quickly and helped us to understand a few elementary procedures at a very reasonable cost. We would highly recommend you to others who suffer computer problems and no doubt we will require your services in the future.

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