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.