[ SOURCE: http://www.secureroot.com/security/advisories/9755048865.html ] -----BEGIN PGP SIGNED MESSAGE----- Microsoft Security Bulletin (MS00-089) - -------------------------------------- Patch Available for "Domain Account Lockout" Vulnerability Originally posted: November 21, 2000 Summary ======= Microsoft has released a patch that eliminates a security vulnerability in Microsoft(r) Windows 2000. The vulnerability could allow a malicious user to use repeated attempts to guess an account password even if the domain administrator had set an account lockout policy. Frequently asked questions regarding this vulnerability and the patch can be found at http://www.microsoft.com/technet/security/bulletin/fq00-089.asp Issue ===== A flaw in the way that NTLM authentication operates in Windows 2000 could allow a domain account lockout policy to be bypassed on a local Windows 2000 machine, even if the domain administrator had set such a policy. The ability of a malicious user to avoid the domain account lockout policy could increase the threat from a brute force password-guessing attack. This vulnerability only affects Windows 2000 machines that are members of non-Windows 2000 domains. In addition, the vulnerability only affects domain user accounts that have previously logged into the target machine and already have cached credentials established on that machine. If a domain account lockout policy is in place and an attacker attempts a brute force password-guessing attack, the domain user account will be locked out as expected at the domain controller. However, if the attacker is able find the correct password, the local Windows 2000 machine will log the attacker on using cached credentials in violation of the account lockout policy. Although the attacker would be able to log on to the local machine, he or she would not be able to authenticate to the domain or gain access to resources on other machines in the domain. Affected Software Versions ========================== - Microsoft Windows 2000 Professional, Service Pack 1 - Microsoft Windows 2000 Server, Service Pack 1 - Microsoft Windows 2000 Advanced Server, Service Pack 1 - Microsoft Windows 2000 Datacenter, Service Pack 1 Note Windows 2000 Gold is not affected by this vulnerability. Patch Availability ================== - http://www.microsoft.com/Downloads/Release.asp?ReleaseID=25606 Note: Windows 2000 users connected to a Windows 2000 domain, stand alone Windows 2000 machines, and users of NT 4.0 do not need to take any action. Note: The Windows 2000 patch can be applied to systems running Windows 2000 Service Pack 1. Users of Windows 2000 Gold are not affected and do not need to take any action. This patch will be included in Windows 2000 Service Pack 2. Note: Additional security patches are available at the Microsoft Download Center More Information ================ Please see the following references for more information related to this issue. - Frequently Asked Questions: Microsoft Security Bulletin MS00-089, http://www.microsoft.com/technet/security/bulletin/fq00-089.asp - Microsoft Knowledge Base article Q274372 discusses this issue and will be available soon. - Microsoft TechNet Security web site, http://www.microsoft.com/technet/security/default.asp Obtaining Support on this Issue =============================== This is a fully supported patch. Information on contacting Microsoft Product Support Services is available at http://support.microsoft.com/support/contact/default.asp. Acknowledgments =============== Microsoft thanks Finch Brett (mailto:brett.finch@hrs.ualberta.ca), Human Resources, University of Alberta, for reporting this issue to us and working with us to protect customers. Revisions ========= - November 21, 2000: Bulletin Created. - --------------------------------------------------- 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. 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