CNET Security Center: Your complete source of antivirus and Internet security information.

Threat meter level and individual ratings
CNET's Internet Threat Watch changes with respect to the level of malicious code on the Internet. The ratings are derived from a variety of public and private computer security sources, and they reflect an aggregate level of malicious activity on the Internet. At CNET we use a 10-point threat rating for individual alerts based upon reports from various computer security sources worldwide. The ratings reflect the threat to your PC and Internet access. For example, 2004's MSBlast worm rated 7 on our scale because it caused localized Internet disruptions worldwide. On the other hand, a recent exploit for a flaw in Mac OS X 10.4 rated only 4 because it simply spread by e-mail but did no other damage and posed no threat to your personal information.