You must protect your computer from any unwanted access. Unwanted access could mean a program that has been loaded onto your computer without your permission, for example a virus downloaded to your computer from an email.
As a minimum we recommend:
Keep your computer software including your browser and operating system up-to-date by installing any security patches or upgrades your supplier recommends. You may find the following links useful:
www.microsoft.com/security
www.mozilla.org/support
www.apple.com/support
Install anti-virus and anti-spyware software on your computer. You should also install a personal firewall. There are many packages available, but whichever you choose it is important that you keep it up-to-date. We can't recommend or approve any specific software. However you may find the following links useful:
www.zonelabs.com
www.symantec.com
www.sophos.com
www.mcafee.com
www.f-secure.com