A computer virus can infect one computer or spread to other computers, and the term virus may refer to malware, spyware, Trojan horses and different types of viruses.
Some computer viruses are merely annoying wheras others can actually damage data on your computer, or even on a computer network.
The best way to protect your computer is to install a reputable antivirus software program such as Norton antivirus, the latest being Norton 360. And remember to download the latest updates so that you can be protected by any new viruses.
One last suggestion: by downloading Norton safe web, you can be protected while browsing the net. Norton safe web or safe web lite will display OK or a question mark letting you know if the website is safe to visit. If the site is not rated and has a question mark, avoid the site especially if you're not familiar with it.