Downadup is second to the notorius SQL slammer worm that devastated the Internet in 2003 . It exploits a bug in the Windows Server service used by Windows 2000, XP, Vista, Server 2003 and Server 2008. It spreads primarily through a buffer overflow vulnerability in Windows Server Service where it disables the operating system update service, security center, including Windows Defender, and error reporting. Its difficult to remove because of its in-built update service .
Its devastation was so terrible that Microsoft had to implement a hotline to enable people to report about Conficker developers .
Finally , BitDefender seems to have come with a solution .It claims to have made the first vaccination tool to remove the Conficker virus .
The downadup removal tool is available here .