This week marks the third anniversary of the first in the wild samples of Conficker appearing on the internet. Conficker is the most recent widespread network worm that began to spread to millions of unpatched PCs in 2008. It spread by exploiting a buffer overflow vulnerability in the Windows Server service. The flaw was patched by Microsoft on October 23, 2008, 29 days before Conficker began it assault. At its peak Conficker infected more than 11 million PCs globally. The Conficker Working Group estimates that 3,250,000 computers are still infected.”]
Source: https://nakedsecurity.sophos.com/2011/11/24/the-conficker-worm-three-years-and-counting/