Windows 95 Update Prevents Sending Clear-Text Password Over Net

Last reviewed: March 18, 1998
Article ID: Q165403
The information in this article applies to:
  • Microsoft Windows 95
  • Microsoft Windows 95 OEM Service Release versions 1, 2, 2.1

SYMPTOMS

Using a program specifically designed for such a purpose, it may be possible to force a Windows 95-based computer running the Microsoft Client for Microsoft Networks to send a user's logon name and password across the network in a clear-text format, instead of the normal encrypted format. It may then be possible to intercept and read that password using such a program.

CAUSE

When a Windows 95-based computer running the Microsoft Client for Microsoft Networks (which uses the SMB file-sharing protocol) connects to an SMB server, a negotiation takes place to determine which dialect of the SMB protocol will be used for communication. Microsoft Networking clients and servers generally support the ability to use older SMB dialects to support interoperability with older products. Some of these older dialects do not support sending passwords over the network in an encrypted form. When such a dialect is negotiated, passwords are sent over the network in clear-text form.

RESOLUTION

This issue is resolved by the following updated files for Windows 95:

   Vredir.vxd version 4.00.1114 (dated 6/2/97) and later
   Vnetsup.vxd version 4.00.1112 (dated 6/2/97) and later

To install this update, follow these steps:

  1. Download the Vrdrupd.exe file to an empty folder.

  2. In My Computer or Windows Explorer, double-click the Vrdrupd.exe file you downloaded in step 1.

  3. Follow the instructions on the screen.

The following file is available for download from the Microsoft Software Library:

 ~ Vrdrupd.exe (size: 215728 bytes) 

For more information about downloading files from the Microsoft Software Library, please see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q119591
   TITLE     : How to Obtain Microsoft Support Files from Online Services

The following files are installed by Vrdrupd.exe:

   File name     Version    Date/Time        Size     Destination folder
   ---------------------------------------------------------------------
   Vredir.vxd    4.00.1114  6/2/97 11:14a    156,773  Windows\System
   Vnetsup.vxd   4.00.1112  6/2/97 11:12a     17,595  Windows\System

MORE INFORMATION

With this update installed, connecting to older SMB servers using the Client for Microsoft Networks is no longer possible, because these older servers do not support encryption of passwords sent over the network.

The following SMB servers are known not to support password encryption over the network:

  • LAN Manager for UNIX (including Hewlett-Packard LM/X)
  • Samba (unless configured for Challenge/Response password encryption)

For additional information about security in Microsoft products, see the following Microsoft Web site:

   http://www.microsoft.com/security/

For additional information about this issue as it applies to Microsoft Windows NT 4.0, see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q166730
   TITLE     : With Unencrypted Password SP3 Fails to Connect to SMB
               Server

For additional information about issues resolved by updates to these components, see the following articles in the Microsoft Knowledge Base:

   ARTICLE-ID: Q165402
   TITLE     : Windows 95 Update to Encrypt Passwords in Memory

   ARTICLE-ID: Q161100
   TITLE     : File May Be Truncated When Copied to a Full Network
               Drive

   ARTICLE-ID: Q157114
   TITLE     : "Access Denied" Attempting to Run File on LM/X Server

   ARTICLE-ID: Q156497
   TITLE     : Duplicate Print Output on PC-LAN Server from Windows 95
               Client

   ARTICLE-ID: Q140558
   TITLE     : Deleting Files on Samba Servers May Delete Local Files
               Instead

   ARTICLE-ID: Q138249
   TITLE     : Updated Vredir.vxd Corrects Errors Running Files on LMX

   ARTICLE-ID: Q160807
   TITLE     : Cannot Connect to Windows NT Server with Many Shares

   ARTICLE-ID: Q150215
   TITLE     : Disabling Automatic Network Shortcut Resolution

   ARTICLE-ID: Q138014
   TITLE     : File May Be Truncated to Zero Bytes When Copied Onto
               Itself

   ARTICLE-ID: Q136834
   TITLE     : Error Copying Read-Only Files to Core SMB Server


Additional query words: 95
Keywords : osr1 osr2 win95 kbfile kbnetwork kbfixlist
Version : 95
Platform : WINDOWS


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Last reviewed: March 18, 1998
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