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FIX: You cannot track the source of failed logon attempts that are made through Threat Management Gateway 2010

SYMPTOMS
When a Microsoft Forefront Threat Management Gateway (TMG) 2010 web proxy or web publishing client tries to authenticate to TMG but provides incorrect credentials, the TMG logs cannot be used to identify the source of the request. 
CAUSE
This issue occurs when an authentication attempt that is made to TMG fails. When this occurs, the request is handled as an anonymous request and will appear in the web proxy logs with the username logged as Anonymous.

The Security event logs on the TMG server will log an "Event ID 4265 Failed Logon attempt," include the domain and username, and state that the authentication attempt originated from the Firewall Service (wspsrv.exe). Because the originating request is logged in the web proxy logs as Anonymous, the TMG logs cannot be used to identify the request that caused the failed authentication attempt.

Where an account lockout occurs after several failed authentication attempts that are made by incoming web proxy or web publishing requests (for example, an ActiveSync device that has a user's old password saved), you cannot identify the source of that request from the TMG logs.
RESOLUTION
To resolve this problem, install the service pack that is described in the following Microsoft Knowledge Base article:
2555840 Description of Service Pack 2 for Microsoft Forefront Threat Management Gateway 2010
By default, the change in behavior is not enabled, and the following script should be run to enable the new behavior. After you enable the new behavior, TMG will log the username that is associated with a failed logon attempt in the Username field as follows, instead of being logged as Anonymous:
domain\username (!)

The "(!)" that is appended to the username indicates that authentication was tried for this user for this request but that the authentication failed. The request will still be treated as Anonymous by TMG in all other aspects, such as rule processing.

To enable this functionality, follow these steps:
  1. Copy the following script into Notepad, and then save it by using the file name EnableFix.vbs:
    set curArray = CreateObject("FPC.Root").GetContainingArray()Const SE_VPS_GUID = "{143F5698-103B-12D4-FF34-1F34767DEabc}"Const SE_VPS_NAME = "LogUsernameForFailedAuthentication"Const SE_VPS_VALUE = 1 Sub SetValue() ' Create the root obect.Dim root ' The FPCLib.FPC root objectSet root = CreateObject("FPC.Root")'Declare the other objects needed.Dim array ' An FPCArray objectDim VendorSets ' An FPCVendorParametersSets collectionDim VendorSet ' An FPCVendorParametersSet object' Obtain references to the array object' and the network rules collection.Set array = curArray Set VendorSets = array.VendorParametersSetsOn Error Resume NextSet VendorSet = VendorSets.Item( SE_VPS_GUID )If Err.Number <> 0 ThenErr.Clear' Add the itemSet VendorSet = VendorSets.Add( SE_VPS_GUID )CheckErrorWScript.Echo "New VendorSet added... " & VendorSet.NameElseWScript.Echo "Existing VendorSet found... value- " & VendorSet.Value(SE_VPS_NAME)End Ifif VendorSet.Value(SE_VPS_NAME) <> SE_VPS_VALUE ThenErr.ClearVendorSet.Value(SE_VPS_NAME) = SE_VPS_VALUEIf Err.Number <> 0 ThenCheckErrorElseVendorSets.Save false, trueCheckErrorIf Err.Number = 0 ThenWScript.Echo "Done with " & SE_VPS_NAME & ", saved!"End IfEnd IfElseWScript.Echo "Done with " & SE_VPS_NAME & ", no change!"End IfEnd SubSub CheckError()If Err.Number <> 0 ThenWScript.Echo "An error occurred: 0x" & Hex(Err.Number) & " " & Err.DescriptionErr.ClearEnd IfEnd SubSetValue
  2. Run the script on one of the TMG array members. The script change will take effect when the TMG configuration synchronizes. No Firewall service restart is necessary for the change to take effect.
  3. To revert the change and to return to the original behavior, locate the following line in the script:
    Const SE_VPS_VALUE = 1
  4. Change that line as follows:
    Const SE_VPS_VALUE = 0
  5. Save the script, and then run the script on one of the array members.
STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
MORE INFORMATION
This new functionality is intended to support the identification of failed authentication attempts that are validated against Active Directory. The new functionality specifically supports the following authentication options:
  • Forward web proxy: NTLM authentication
  • Forward web proxy: Basic authentication
  • Web publishing: NTLM authentication
  • Web publishing: Basic authentication
  • Web publishing: Forms-based authentication with Active Directory
  • Web publishing: Forms-based authentication with LDAP
REFERENCES
For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates

TMG TMG2010
Properties

Article ID: 2592929 - Last Review: 10/31/2011 07:55:00 - Revision: 2.0

  • Microsoft Forefront Threat Management Gateway 2010 Enterprise
  • Microsoft Forefront Threat Management Gateway 2010 Standard
  • Microsoft Forefront Threat Management Gateway 2010 Service Pack 1
  • kbfix kbbug kbexpertiseinter kbsurveynew KB2592929
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