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             AUSCERT External Security Bulletin Redistribution

            Vulnerability in SMB Could Allow Denial of Service
                             14 November 2009


        AusCERT Security Bulletin Summary

Product:           SMB
Publisher:         Microsoft
Operating System:  Windows 7
                   Windows Server 2008
Impact/Access:     Denial of Service -- Remote with User Interaction
Resolution:        Mitigation
CVE Names:         CVE-2009-3676  

Reference:         http://www.auscert.org.au/11954

Original Bulletin: 

Comment: Please note it is Server 2008 R2 that is affected, along with
         Windows 7.
         Exploit code for this vulnerability has been made public.

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Microsoft Security Advisory (977544)

Vulnerability in SMB Could Allow Denial of Service
   Published: November 13, 2009

   Version: 1.0

General Information

Executive Summary

   Microsoft is investigating new public reports of a possible denial of 
   service vulnerability in the Server Message Block (SMB) protocol. This 
   vulnerability cannot be used to take control of or install malicious 
   software on a users system. However, Microsoft is aware that detailed 
   exploit code has been published for the vulnerability. Microsoft is not 
   currently aware of active attacks that use this exploit code or of 
   customer impact at this time. Microsoft is actively monitoring this 
   situation to keep customers informed and to provide customer guidance as 

Affected Software

   Windows 7 for 32-bit Systems
   Windows 7 for x64-based Systems
   Windows Server 2008 R2 for x64-based Systems*
   Windows Server 2008 R2 for Itanium-based Systems

   *Server Core installation affected.


   Block TCP ports 139 and 445 at the firewall

   These ports are used to initiate a connection with the affected component. 
   Blocking TCP ports 139 and 445 at the firewall will help protect systems 
   that are behind that firewall from attempts to exploit this vulnerability. 
   Microsoft recommends that you block all SMB communications to and from the 
   Internet to help prevent attacks. For more information about ports, see 
   TCP and UDP Port Assignments.

   Impact of Workaround: Several Windows services use the affected ports. 
   Blocking connectivity to the ports may cause various applications or 
   services to not function. Some of the applications or services that could 
   be impacted are listed below:
   Applications that use SMB (CIFS)
   Applications that use mailslots or named pipes (RPC over SMB)
   Server (File and Print Sharing)
   Group Policy
   Net Logon
   Distributed File System (DFS)
   Terminal Server Licensing
   Print Spooler
   Computer Browser
   Remote Procedure Call Locator
   Fax Service
   Indexing Service
   Performance Logs and Alerts
   Systems Management Server
   License Logging Service   

   How to undo the workaround. Unblock TCP ports 139 and 445 at the firewall.

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