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Computer viruses are software programs deliberately designed to interfere with computers, disrupt or delete data and spread themselves - via email, downloads and files - to other computers online and throughout the internet.

As technology advances so does the sophistication of the virus. Viruses can arrive via a corrupted disk or program, emails attachments, installing software from CD-ROM, DVD-ROM, floppy disk or a USB flash device, by wireless transfer, such as InfraRed or Bluetooth, and in every kind of internet download.

What is a virus?

A virus is a computer program that downloads itself on to your PC with the intent of carrying out a malicious act. They can be slightly troublesome or potentially disastrous, for example, deleting all your files from the computer's hard drive. Some viruses cause harm to your PC while others are made for the sole use of criminal activity. Most viruses replicate themselves.

What is a worm?

A worm is a type of virus. It acquired its name because it infects a system gradually, like a worm eating an apple. Most worms will try to infect as many computer files as possible, including free space. Other worms duplicate by attaching themselves to email, which is then automatically sent out, or to other file transfers.

What is a trojan?

A trojan horse is a destructive program masquerading as a beneficial one. This virus might not be self-replicating, but it is often used as a vehicle for a virus that then infects your computer - just as the original wooden horse 'gift' contained Greek soldiers. An example of a trojan is a download that claims to get rid of computer viruses and then installs a virus on your PC instead.

What can I do?

A virus can cause irreparable damage to your computer, so virus prevention is definitely better than a cure.