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MS02-070: Flaw in SMB Signing May Permit Group Policy to Be ModifiedArticle ID: 329170 - View products that this article applies to. This article was previously published under Q329170 On This PageSYMPTOMSSupport for the Server Message Block (SMB) protocol is
included in all versions of Windows. Although SMB is a file-sharing protocol,
SMB is also used for other purposes. One of these purposes is disseminating
Group Policy settings from domain controllers to computers that log on.
Beginning with Windows 2000, it is possible to improve the integrity of SMB
sessions by digitally signing all packets in a session. Windows 2000 and
Windows XP can be configured to always sign, never sign, or sign only if the
other party requires it. A flaw in the implementation of SMB signing in Windows 2000 and Windows XP can permit an attacker to silently downgrade the SMB signing settings on an affected computer. To do this, an attacker must have access to the session negotiation data as it is exchanged between a client and server, and must be able to modify the data in a way that exploits the flaw. This can cause either or both computers to send unsigned data no matter what signing policy the administrator sets. After the attacker downgrades the signing setting, the attacker can continue to monitor and change data in the session. The lack of signing prevents the communicators from detecting the changes. Although this vulnerability can be exploited to expose any SMB session to tampering, the most serious case involves changing Group Policy settings as they are disseminated from a Windows 2000-based domain controller to a newly logged-on network client. By doing this, an attacker can take actions such as adding users to the local Administrators group or installing and running code on the computer. Note that Windows XP cannot be used as a domain controller. Therefore, this scenario does not apply to Windows XP. This is the highest-risk scenario that is associated with the vulnerability. RESOLUTIONWindows XP service pack informationTo resolve this problem, obtain the latest service pack for Microsoft Windows XP. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:322389
(http://support.microsoft.com/kb/322389/EN-US/
)
How to obtain the latest Windows XP service packWindows XP hotfix informationDownload informationThe following files are available for download from the Microsoft Download Center:32-bit: Collapse this image 
(http://www.microsoft.com/downloads/details.aspx?FamilyID=77b49431-742b-4426-ad45-f09d3aed16cb&DisplayLang=en)
64-bit:
Release Date: December 11, 2002Collapse this image
(http://microsoft.com/downloads/details.aspx?FamilyId=580FCE68-B7E2-4BF9-8A16-54D1E39F2168&displaylang=en)
For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base: 119591
Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help to prevent any unauthorized changes to the file.
(http://support.microsoft.com/kb/119591/EN-US/
)
How to Obtain Microsoft Support Files from Online Services
Restart requirementYou must restart your computer after you apply this update.Installation informationThis update supports the following Setup switches:
q329170_wxp_sp2_x86_enu /q /u /z Warning Your computer is vulnerable until you restart it. File informationThe English version of this fix has the file attributes (or later) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.The following files are installed in the %Windir%\System32\Drivers folder. Windows XP Date Time Version Size File name -------------------------------------------------------------- 31-Oct-2002 19:45 5.1.2600.105 322,304 Srv.sys Windows XP SP1, Windows XP Tablet PC Edition Date Time Version Size File name -------------------------------------------------------------- 20-Dec-2002 17:36 5.1.2600.1154 322,048 Srv.sys Windows XP 64-Bit Edition Date Time Version Size File name -------------------------------------------------------------- 31-Oct-2002 19:45 5.1.2600.105 1,142,016 Srv.sys Windows XP 64-Bit Edition SP1 Date Time Version Size File name -------------------------------------------------------------- 20-Dec-2002 17:36 5.1.2600.1154 1,140,480 Srv.sys Windows 2000 service pack informationTo resolve this problem, obtain the latest service pack for Microsoft Windows 2000. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:260910
(http://support.microsoft.com/kb/260910/EN-US/
)
How to Obtain the Latest Windows 2000 Service Pack
Windows 2000 hotfix informationDownload informationThe following files are available for download from the Microsoft Download Center:All Languages except NEC Japanese: Collapse this image
(http://microsoft.com/downloads/details.aspx?FamilyId=52EAC216-A360-4E2D-9C6B-AD4D31C40BA2&displaylang=en)
NEC Japanese:
Release Date: December 11, 2002Collapse this image
(http://microsoft.com/downloads/details.aspx?FamilyId=F4119765-846B-491C-B162-BE06BD432828&displaylang=ja)
For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base: 119591
Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help to prevent any unauthorized changes to the file.
(http://support.microsoft.com/kb/119591/EN-US/
)
How to Obtain Microsoft Support Files from Online Services
Restart requirementBecause of file dependencies, this update requires Windows 2000 Service Pack 2 (SP2) or Service Pack 3 (SP3). For additional information, click the article number below to view the article in the Microsoft Knowledge Base:260910
(http://support.microsoft.com/kb/260910/EN-US/
)
How to Obtain the Latest Windows 2000 Service Pack
Installation InformationYou must restart your computer after you apply this update. This update supports the following Setup switches:
q329170_w2k_sp4_x86_en /q /u /z Warning Your computer is vulnerable until you restart it. File InformationThe English version of this fix has the file attributes (or later) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.The following files are installed in the %Windir%\System32\ folder: Date Time Version Size File name ------------------------------------------------------------ 01-Nov-2002 16:55 5.0.2195.6090 250,640 Localspl.dll 01-Nov-2002 16:55 5.0.2195.6023 381,712 Printui.dll 23-Oct-2002 15:05 5.0.2195.6100 138,752 Sp3res.dll 01-Nov-2002 16:55 5.0.2195.6047 79,632 Spoolss.dll 31-Oct-2002 00:45 5.0.2195.6110 237,456 Srv.sys 01-Nov-2002 16:55 5.0.2195.6110 74,000 Srvsvc.dll 01-Nov-2002 16:55 5.0.2195.6044 84,752 Win32spl.dll 01-Nov-2002 16:55 5.0.2195.6032 114,448 Winspool.drv 01-Nov-2002 16:55 5.0.2195.6103 55,056 Wlnotify.dll STATUS
Microsoft has confirmed that this problem may cause a degree of security vulnerability in the Microsoft products that are listed in the "Applies to" section.
Windows XPThis problem was first corrected in Microsoft Windows XP Service Pack 2.Windows 2000This problem was first corrected in Microsoft Windows 2000 Service Pack 4.MORE INFORMATION For more information about this vulnerability, visit the
following Microsoft Web site: http://www.microsoft.com/technet/security/bulletin/MS02-070.mspx
(http://www.microsoft.com/technet/security/bulletin/MS02-070.mspx)
PropertiesArticle ID: 329170 - Last Review: December 1, 2007 - Revision: 14.6 APPLIES TO
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