Microsoft issued a new security alert on October 23rd just in time for Halloween. You can check out the details at http://www.microsoft.com/technet/security/Bulletin/MS08-067.mspx

In the meantime, I’ll give you a quick rundown.

What is the Vulnerability?  An error in the way that the Server Service handles a Remote Procedure Call (RPC) request could allow for remote code execution if an affected system received a specially crafted RPC request without the need for authentication on the victim system documented in MS08-067 bulletin.

The Microsoft Security Bulletin (MS08-067) listed the vulnerability as critical. If not corrected then your server could be vulnerable to remote code execution. (Article ID: 958644)

The security update resolves a privately reported vulnerability in the Server service. On Microsoft Windows 2000, Windows XP, and Windows Server 2003 systems, an attacker could exploit this vulnerability without authentication to run arbitrary code. It is possible that this vulnerability could be used in the crafting of a worm exploit. Firewall best practices and standard default firewall configurations can help protect network resources from attacks that originate outside the enterprise perimeter.

This security update is rated Critical for all supported editions of Microsoft Windows 2000, Windows XP, Windows Server 2003, and rated Important for all supported editions of Windows Vista and Windows Server 2008.

The security update addresses the vulnerability by correcting the way that the Server service handles RPC requests. For more information about the vulnerability, see the Frequently Asked Questions (FAQ) subsection for the specific vulnerability entry under the section, Vulnerability Information, on the Microsoft web page for this security alert.

If you’re unfamiliar with RPC requests I’ll give you a brief explanation. A Remote Procedure Call (RPC) is a protocol that one program can use to request a service from a program located in another computer in a network. Since RPC uses the client/server model the requesting program is a client and the service-providing program is the server.

And like a regular or local procedure call, an RPC is a synchronous operation which means that the requesting program is suspended until the results of the remote procedure are returned.