We have discovered a critical security vulnerability in all recent versions of Microsoft operating systems. The vulnerability affects default installations of Windows NT 4.0, Windows 2000, Windows XP as well as Windows 2003 Server. This is a buffer overflow vulnerability that exists in an integral component of any Windows operating system, the RPC interface implementing Distributed Compon ent Object Model services (DCOM). In a result of implementation error in a function responsible for instantiation of DCOM objects, remote attackers can obtain unauthorized access to vulnerable systems. The existence of the vulnerability has been confirmed by Microsoft Corporation. The appropriate security bulletin as well as fixes for all affected platforms are available for download from http://www.microsoft.com/security/ (MS03-026). It should be emphasized that this vulnerability poses an enormous threat and appropriate patches provided by Microsoft should be immediately applied. We have decided not to publish codes or any technical details with regard to this vulnerability at the moment. With best regards, Members of The Last Stage of Delirium Research Group http://lsd-pl.net