The late '90s and all of the 2000s were a rough time for Microsoft as Windows and other Microsoft programs were hit with a string of security problems, such as high-profile virus attacks including Melissa, ILoveYou, Blaster, Code Red, and Nimda. The Cult of the Dead Cow came back to Defcon armed with Back Orifice 2000 (or BO2k), an updated version of its remote system administration tool that included support for Windows NT, Windows 2000 and Windows XP. Malware cropped up that exploited Internet Information Server (IIS) services, including a nasty buffer overflow technique. Among the various problems was an exploit that allowed attackers to take control of Windows 2000 servers via IIS, a serious flaw in Windows 2000 that could enable remote intruders to access a PC via its Internet Protocol address and a Plug-and-Play vulnerability in Windows 2000 that was exploited by a series of worms in what experts said appeared to be a war between different virus writer groups. Attackers also were found to be exploited an unpatched security flaw in the Domain Name System (DNS) service.