One way which viruses are distributed are through system script files such as files with VBS and JS extensions. One on the more well known attacks which used this method is the ILOVEYOU virus which spread as an email attachment and counted on the user running the script file attachment.

To help protect yourself from these types of attacks, check out Script Defender. The concept is simple:

AnalogX Script Defender will intercept any request to execute the most common scripting types used in virus attacks, such as Visual Basic Scripting (.VBS), Java Script (.JS), etc., and can even be configured to intercept new script extensions as needed! It’s very simple to use and helps to ensure that you do not inadvertently run a script no matter what email program you use, or even if you get it via another method.

Simple and effective. For the most part, very seldom would an average user ever run a script file, so having this on end user systems makes sense.