Virus

What is a virus? In reality, simple viruses are now rare and have been replaced by more complex malicious attacks, but a virus is a piece of computer code that can copy or "replicate" itself, "infecting" your PC without your knowledge. Viruses are usually harmful to the information and files stored on your computer. Common ways for files to become infected by viruses are from downloading email attachments and web programmes, such as screen savers.

Top tip: to protect yourself against virus attacks, you must have a regularly updated antivirus program installed on your PC.

Firewall

A personal firewall, combined with up-to-date antivirus software, is the best way to protect your home computer against malicious attacks. A personal firewall acts as a guard, keeping constant watch over the information coming through your Internet connection and preventing unauthorised access to your computer. It can prevent your computer from being accessed in ways you've not approved or that are often used by viruses or hackers.

Top tip: to fully protect yourself online, in addition to updated antivirus software, you should also have a personal firewall installed on your PC. You can buy fully integrated security programmes, which include these and other essential security functions in one package.

Spam

Spam is any unwanted electronic mail and has become one of the most notorious downsides to online life. A persistent inconvenience, it's also become a common tool for malicious activity. Virus writers use spam to distribute harmful code, and con artists are targeting their would-be victims through "phishing" expeditions. It can be difficult to stop spam but there are anti-spam programs available that can help combat the problem.

Top tip: never respond to spam, even to ask to be removed from a list, as this will confirm that your email address is real and active. Delete it straight away.

Phishing

Phishing is a technique where fraudsters disguise themselves as well-known companies and trick people into divulging confidential data. It has proved to be a significant issue for some banks and online retailers, who have had customers that have been tricked into giving private information to criminals. Computer users should be wary of emails asking for confidential or personal information and make sure that they are legitimate before responding.

Top tip: never give personal information in an email. Legitimate businesses and banks would not ask for bank or personal details over email.

Trojan Horse

Trojan horses are malicious programs disguised as something harmless. They've been known to pose as games, utilities, and email attachments. Once opened, Trojan horses act differently than expected. Some merely annoy, sending emails to everyone in your address book, for example. Others do serious damage, including stealing passwords and data files.

Top tip: be very careful when downloading files or opening email attachments. If you are unsure of the source, DON'T do it! Make sure you have an integrated security package on your PC, and that it is regularly updated, to protect you from infection by malicious code.

Spyware

Spyware is perhaps best described as split-personality software. It resides on your computer and usually has a practical and attractive set of primary features. Its core functionality has nothing to do with spying, it might be a utility or an mp3 player or some kind of game, and it's usually offered as freeware (software that you can download from the Web for free). The problem is, in addition to its primary features, spyware also has a second, less conspicuous component. This second component gathers information about your computing habits and sends that information over the Internet to the software's publisher. Because this secondary action often goes on without your knowledge, software with this kind of dual functionality has come to be known as spyware.

Top tip: be very careful when downloading files or programmes from the Internet, and always check the small print (end user license agreements) before you click "OK". Choose a security solution that incorporates spyware protection as well as other vital security functions.

Worms

Worms are a type of virus that can locate victims and spread to them independently over a network, including the Internet. Unlike true viruses, worms are themselves small programs that don't require another file to infect or any user interaction to operate. Worms can cause direct harm by infecting your PC and if widespread, can cause indirect harm due to their ability to spread so rapidly that they cause your computer to slow down or not operate properly. In recent months there has been an increase in the number of advanced, malicious worms directed at both home and business users.

Top tip: ensure you have fully updated antivirus and personal firewall software and raise the alarm if your PC seems to be operating abnormally slowly.