A Computer Virus is a software program that is designed to copy itself over and over again and to attach itself to other programs.

It is important to understand that viruses do not damage the hardware. They affect the data and programs stored on your computer.

The most common way of getting a virus these days is to open an email attachment or visit a web page which contains a virus. Another way is to load an infected file into your computer from some kind of storage device:

•floppy disk •memory stick •CDROM •DVDBasically a virus is spread by allowing it to run on your computer, so any executable file or computer program can contain a virus.

As computer viruses became more of a menace, companies began to develop software to detect and remove them. These were named 'anti-virus software'.

When the anti-virus software recognises a virus pattern, it will alert the user, and ask them whether they want to remove the virus and clean the system, or whether they simply want to 'quarantine' the virus.

Viruses can be prevented by taking sensible precautions including:

-Scanning all incoming e-mails - Use special filtering software to prevent automatic downloads of computer programs - Not allowing people to load applications or use floppy disks/memory sticks on your system- Not using software that has been copied - Backing up your system regularly so you can recover your data with clean copies

As the internet has grown and millions of people are online, so has the development of other types of software pests. These include:

Trojan software•Log all your keystrokes and then send the details to a remote computer / server. Used to capture your passwords •Allow someone else to take control of your computer whilst you are online. •Capture screen shots and send them to a remote computer, once again with the intent of obtaining confidential information such as financial screen shots.

It is against the law to distribute a virus to others. The law which covers this area is called The Computer Misuse Act . It also covers various computer crimes such as Hacking, computer fraud as well as the deliberate spread of viruses.

Anyone caught distributing viruses knowingly faces an unlimited fine and up to a five year prison sentence.

Almost one million Chinese computers were hit by viruses during last week's national holidays, state media has reported. Three different types of viruses attacked computers during the holiday week, Xinhua news agency said. China has more than 130 million internet users and last week should have been a perfect time for them to catch up with their web surfing. There was an entire week of national holidays known as the Golden Week, so most people were off work with plenty of time to spend at home online.

A Windows virus that warns users about illegal net use is spreading online. The bug-bearing message claims to come from either the FBI, CIA or German BKA police agency. It warns users they have been detected visiting illegal sites. Those opening a questionnaire attached to the message will be infected by a variant of the well-known Sober virus. Anti-virus firms have caught millions of copies of the malicious program, suggesting a lot of people have fallen for the fake warning.

Users of America Online's instant messenger are being warned about a worm spreading via the chat network. The Windows worm installs spyware programs and turns over control of the machine to the creator of the virus. Studies show that malicious programs designed to attack instant message networks have grown dramatically over the past 12 months. But some security firms say the threat to users of these chat systems is still relatively low.

Malicious hackers have turned to Wikipedia to try to help them catch out PC users.The virus writers created a page on the German Wikipedia that linked to a fake fix for a new version of an old malicious Windows worm. But instead of curing a bug, those installing the fix would be infected by a new Windows virus.

Virus writers are exploiting Sony's controversial anti-piracy software to hide their malicious creations. In late October Sony was found to be using stealth techniques to hide software that stopped some of its CDs being illegally copied. Now three virus variants have been found that use the Sony software to evade detection by anti-virus programs.