Thousands of organizations used that list, and the expanded Top-20 lists that followed one, two, and three years later, to prioritize their efforts so they could close the most dangerous holes first. The vulnerable services that led to worms like Blaster, Slammer, and Code Red have been on these lists.
This SANS Top-20 2005 is a marked deviation from the previous Top-20 lists. In addition to Windows and UNIX categories, SANS has also included Cross-Platform Applications and Networking Products. The change reflects the dynamic nature of the evolving threat landscape. Unlike the previous Top-20 lists, this list is not "cumulative" in nature. It only has critical vulnerabilities from the past year and a half or so.
The Top-20 2005 is a consensus list of vulnerabilities that require immediate remediation. It is the result of a process that brought together dozens of leading security experts. They come from the most security-conscious government agencies in the UK, US, and Singapore; the leading security software vendors and consulting firms; the top university-based security programs; many other user organizations; and the SANS Institute.