What is a Virus, Trojan, Worm, or Malware?

If you read the newspaper, watch the news, or use a computer then you may have heard about viruses and other malware, They are those malicious programs that once they infect your computer will begin creating havoc for your machine. What most people do not know is that there is many different types of viruses categorized in the general category of Malware.

Malware - Malware is programming or files that are developed for doing harm. Thus, malware includes computer viruses, Trojan horses, spyware, worms, hijackers, and certain types of adware.

This blog is going to focus on malware that is considered a virus, trojan, and worms. Though this information can also be used to remove most other types of malware. I will not be going into specific details about any one particular infection, but rather provide a broad overview of how these infections can be removed. For the most part these instructions should allow you to remove a good deal of infections, but there are some that need special steps to be removed and those won't be covered in this blog.

Adware - A program that generates pop-ups on your computer or displays advertisements. It is important to note that not all adware programs are necessarily considered malware. There are many legitimate programs that are given for free that display ads in their programs in order to generate revenue. As long as this information is provided up front then they are generally not considered malware.


Backdoor - A program that allows a remote user to execute commands and tasks on your computer without your permission. These types of programs are typically used to launch attacks on other computers, distribute copyrighted software or media, or hack other computers.

Dialler - A program that typically dials a premium rate number that has per minute charges over and above the typical call charge. These calls are with the intent of gaining access to pornographic material.

Hijackers - A program that attempts to hijack certain Internet functions like redirecting your start page to the hijacker's own start page, redirecting search queries to a undesired search engine, or replace search results from popular search engines with their own information.

Spyware - A program that monitors your activity or information on your computer and sends that information to a remote computer without your knowledge.

Trojan - A program that has been designed to appear innocent but has been intentionally designed to cause some malicious activity or to provide a backdoor to your system.

Virus - A program that when run, has the ability to self-replicate by infecting other programs and files on your computer. These programs can have many effects ranging from wiping your hard drive, displaying a joke in a small box, or doing nothing at all except to replicate itself. These types of infections tend to be localized to your computer and not have the ability to spread to another computer on their own. The word virus has incorrectly become a general term that encompasses trojans, worms, and viruses.

Worm - A program that when run, has the ability to spread to other computers on its own using either mass-mailing techniques to email addresses found on your computer or by using the Internet to infect a remote computer using known security holes.