The majority of the successful attacks on operating systems come from only a few software vulnerabilities. This can be attributed to the fact that attackers are opportunistic, take the easiest and most convenient route, and exploit the best-known flaws with the . . .
The majority of the successful attacks on operating systems come from only a few software vulnerabilities. This can be attributed to the fact that attackers are opportunistic, take the easiest and most convenient route, and exploit the best-known flaws with the most effective and widely available attack tools. They count on organizations not fixing the problems, and they often attack indiscriminately, scanning the Internet for any vulnerable systems. System compromises in the Solar Sunrise Pentagon hacking incident, for example, and the easy and rapid spread of the Code Red and NIMDA worms can be traced to exploitation of unpatched vulnerabilities.

Two years ago, the SANS Institute and the National Infrastructure Protection Center (NIPC) released a document summarizing the Ten Most Critical Internet Security Vulnerabilities. Thousands of organizations used that list, and the expanded Top Twenty, which followed a year later, to prioritize their efforts so they could close the most dangerous holes first. The vulnerabilities that led to all three examples above - the Solar Sunrise Pentagon incident, and the Code Red and NIMDA worms - are on that list.