First step is to install and maintain anti-virus software. There are plenty of great anti-virus software packages available. This anti-virus software checks for known viruses by scanning your computer periodically. Usually will  check for viruses on incoming email. It is very important to update the software as well though.

New viruses appear almost daily. At least once a week you must check the web site of the company that makes your anti-virus software to see if there is an update available.

Second step is to not open unknown or suspicious e-mail. Usually many viruses and worms use what is called “social engineering”.
That is, they attempt to trick you into becoming a participant in the process. The newest viruses can “spoof” the sending email address so that it looks like it is coming from someone other than the computer that infected it.

If an email is not from someone you know, it is  best to simply delete it without looking at it( without open it). If you are shure that email was send to you  from someone you know, you should read the message carefully before opening any attached files. Viruses and worms often have bad English language and poor grammar. Consider whether the person you know would really have written that message or forwarded you the attached file. If in doubt, contact that person you know to confirm they truly sent it before opening the attachment.

The third step is to keep your computer patched against known vulnerabilities. Almost as often as new viruses appear, new vulnerabilities are discovered as well. Many times they are in the operating system (like Windows, Linux, OS,Dos), but vulnerabilities are also found in tools like your web browser(Internet Explorer, Alta Vista, Netscape..), email software (Outlook Expres)and other 3rd party tools. Left unpatched, these vulnerabilities can be exploited by hackers to obtain access and control of your computer.

Staying up to date can be difficult. Some seller, such as Microsoft, have automated utilities that check for updates and notify you. Other vendors may have an email mailing list you can join so they can notify you of any new updates. If your vendor doesn’t offer solutions, you may just need to periodically check their support web site to look for any new patches or updates.