Virus 101

What is “malware”, and what is the difference between a virus, a worm and a Trojan? Do I need to worry about them? Malware is short for malicious software and is a general term used to cover items such as viruses, worms etc. that are designed to damage your PC. Unfortunately new types of unwanted software are popping up all the time, from the annoying but innocent, such as adverts, to genuinely harmful programs such as viruses.

GMT Solutions: VirusesA virus is a program that infects a PC, spreading from one file to another, and then from one PC to another when files are copied or shared. It is designed to delete or corrupt your files, or make your PC completely unusable.
To protect yourself: make sure you have anti-virus software installed, and that it is downloading the latest updates/definitions.

Worms usually spread through a network or by e-mail, and may be harmless, or they may have a destructive “payload” which deletes files. A common purpose of worms is to put the infected computer under the control of the worm author, so it can be used as part of a “zombie network” to send spam.
To protect yourself: in addition to anti-virus, having a firewall in place will help protect you, and so will applying the latest operating system patches – this fixes any holes in the system that worms use to get in.

Trojan horses are similar to their ancient Greek namesake – they appear to be an innocent application, but install a backdoor in your computer to allow it to be remotely controlled. The difference between a Trojan and a virus is that the Trojans don’t copy themselves, they have to be installed by a user.
To protect yourself: check that any software you are installing is legal and genuine – is a good place to check for genuine versions of free software.

Spyware is pretty much what it sounds like – software that looks at what you do on the computer and sends that information back to a third party. They might be interested in your browsing habits, or worse, your online banking login and credit card information.
To protect yourself: anti-malware software sometimes comes bundled with anti-virus, but a highly recommended free version is Malwarebytes (available from

All this sounds a bit scary – but the good news is, that Windows comes with security tools such as Windows Firewall and Defender, to protect you from all of the above. I would also recommend installing an anti-virus – AVG is a great free version (available from, Kaspersky and Sophos are good paid-for versions and simple to set up.
If you have any queries or need help with malware, please e-mail us at [email protected]