Microsoft Security Bulletin MS01-011

[Microsoft Product Security <secnotif () MICROSOFT COM>]

The following is a Security  Bulletin from the Microsoft Product Security
Notification Service.

Please do not  reply to this message,  as it was sent  from an unattended
mailbox.
                    ********************************

-----BEGIN PGP SIGNED MESSAGE-----

- ----------------------------------------------------------------------
Title:      Malformed Request to Domain Controller can Cause Denial
            of Service
Date:       20 February 2001
Software:   Windows 2000 Server, Advanced Server and Datacenter
            Server
Impact:     Denial of Service
Bulletin:   MS01-011

Microsoft encourages customers to review the Security Bulletin at:
http://www.microsoft.com/technet/security/bulletin/MS01-011.asp.
- ----------------------------------------------------------------------

Issue:
======
A core service running on all Windows 2000 domain controllers (but
not on any other machines) contains a flaw affecting how it processes
a certain type of invalid service request. Specifically, the service
should handle the request at issue here by determining that it is
invalid and simply dropping it; in fact, the service performs some
resource-intensive processing and then sends a response.

If an attacker sent a continuous stream of such requests to an
affected machine, it could consume most or all of the machine's CPU
availability. This could cause the domain controller to process
requests for service slowly or not at all, and could limit the number
of new logons the machine could process and the number of Kerberos
tickets that could be issued.

Mitigating Factors:
====================
 - The machine would automatically resume normal processing
   as soon as the stream of requests ceased.
 - Although the attacker could, in theory, use the vulnerability
   to completely deny service to network users, in practice the
   attack rarely consumes more than 75% of the available CPU
   resources.
 - Users who were already logged on and were using previously
   issued Kerberos tickets would not be affected by domain
   controller unavailability.
 - If there were multiple domain controllers on the domain, the
   unaffected machines could pick up the other machine's load.
 - If normal security practices have been followed, Internet
   users would be prevented by firewalling and other measures
   from levying requests directly to domain controllers.

Patch Availability:
===================
 - A patch is available to fix this vulnerability. Please read the
   Security Bulletin
   http://www.microsoft.com/technet/security/bulletin/ms01-011.asp
   for information on obtaining this patch.


- ---------------------------------------------------------------------

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED
"AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL
WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY
DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL,
CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF
MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION
OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO
THE FOREGOING LIMITATION MAY NOT APPLY.



-----BEGIN PGP SIGNATURE-----
Version: PGP Personal Privacy 6.5.3

iQEVAwUBOpMlb40ZSRQxA/UrAQFjbwgAjvdzymgjQ8uqjz7eskQcODNtQEbGrSOW
eSedq1nM/fmy1dxkR63xZ7BubKJ3H74kkBIL+Pg7/I8laeCFvmBCTFUiD9dFA50P
c67Y5Gj06B98Ns/vgbnrY+WoApV3D8ZmrkX0bVIC1tDpGp2kBCTmJJQKsC/OlYLq
tXI7tsM7ishtRX5FPMTABOP7TkgF2oW6+BU8m3/fzmpNTeByhYImRLGjRZTasvK1
MOaC/NmNmbgBoF+Ntg1Aef3VCcvdfFXoh5rEkpfkfFMVbRcIfPA0kgQmJ5LIGHJi
mCrO0I33+4mMS/+UVVkP7CbUcD37k93pdzX7iHgL/cYuU9i2bFxEPQ==
=0wFd
-----END PGP SIGNATURE-----

   *******************************************************************
You have received  this e-mail bulletin as a result  of your registration
to  the   Microsoft  Product  Security  Notification   Service.  You  may
unsubscribe from this e-mail notification  service at any time by sending
an  e-mail  to  MICROSOFT_SECURITY-SIGNOFF-REQUEST () ANNOUNCE MICROSOFT COM
The subject line and message body are not used in processing the request,
and can be anything you like.

To verify the digital signature on this bulletin, please download our PGP
key at http://www.microsoft.com/technet/security/notify.asp.

For  more  information on  the  Microsoft  Security Notification  Service
please  visit  http://www.microsoft.com/technet/security/notify.asp.  For
security-related information  about Microsoft products, please  visit the
Microsoft Security Advisor web site at http://www.microsoft.com/security.