Given the huge amount of press and industry attention to 'Spyware' it is easy to forget there are other types of malicious software or 'malware' out there. Viruses, Worms and Trojans are still being developed to steal your personal data or damage your computer. These malicious programs can be hidden in email attachments or files which are downloaded off the internet.

Most computer users are familiar with the term 'computer virus.' A Virus is usually hidden within another program or executable file. A Virus can be relatively harmless, for example displaying a message or picture at a preset time. Others variants however can be incredibly destructive including erasing data from your hard drive, corrupting programs or stealing sensitive information like passwords or financial data.

One of the limitations with a Virus is that it cannot spread itself automatically. Unfortunately a 'Worm' can, and it exists to replicate itself. It is a self-contained program which is usually embedded in an email attachment like a Microsoft Word document. The most notorious variants like the 'ILOVEYOU' Worm in 2000 are spread using the e-mail address book on the infected user's computer. It emails itself to the contacts in the address book without the user's knowledge.

A Worm can cause extensive damage to both the computer and the network your computer uses. A Worm infection consumes network bandwidth as it sends itself out. For example, a widespread infection can dramatically slow or totally overload a corporate network. It can even slowdown the speed of the Internet itself!

A Worm can also carry a dangerous program. The most common type of program is a 'backdoor' which given hidden access to your computer to the virus creator. Your computer then becomes a 'Zombie' used to send out Spam e-mail or other computer viruses.
A Trojan masquerades itself as a legitimate program or file. For example, you may think that you are downloading a MP3 music file but when the file is loaded a virus is installed on your system. Once installed onto the user's computer it can have the same impact as a Virus.

Here are some common symptoms of infection by any of they types of malware:
- Unexplained crashes
- Strange program error messages
- Computer freezes
- Poor computer performance
- Angry emails from people you have 'spammed' or unknowingly sent a virus (sign that your computer is a possible 'Zombie').

Here are some steps you can take to help prevent infection:
- Make sure you are receiving the latest Windows XP updates. It is highly recommended that you receive these updates automatically.
- Have a good firewall installedideally you want to have an application which filters both 'inbound' and 'outbound' internet traffic.
- Delete and do not open any email with an attachment from anyone you do not know.
- Install an anti virus program and keep the virus definitions up to date. Carry out a virus scan a least once a week. Always scan email attachments if you are planning on opening them.
- Use a Spam Filter to stop dangerous email getting onto your computer in the first place.