Article ID: 165403 - View products that this article applies to.
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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.
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.
This issue is resolved by the following updated files for Windows 95:
To install this update, follow these steps:
Vredir.vxd version 4.00.1114 (dated 6/2/97) and later Vnetsup.vxd version 4.00.1112 (dated 6/2/97) and later
For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base:
Download Vrdrupd.exe now
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119591Microsoft 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
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
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:
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:
(http://support.microsoft.com/kb/166730/EN-US/ )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:
(http://support.microsoft.com/kb/165402/EN-US/ )Windows 95 Update to Encrypt Passwords in Memory
(http://support.microsoft.com/kb/161100/EN-US/ )File May Be Truncated When Copied to a Full Network Drive
(http://support.microsoft.com/kb/157114/EN-US/ )"Access Denied" Attempting to Run File on LM/X Server
(http://support.microsoft.com/kb/152186/EN-US/ )Possible Network Data Corruption If Locking Not Used
(http://support.microsoft.com/kb/148367/EN-US/ )Possible Network File Corruption with Redirector Caching
(http://support.microsoft.com/kb/142803/EN-US/ )Updated Vredir.vxd Corrects Problems Accessing Database Files
(http://support.microsoft.com/kb/140558/EN-US/ )Deleting Files on Samba Servers May Delete Local Files Instead
(http://support.microsoft.com/kb/138249/EN-US/ )Updated Vredir.vxd Corrects Errors Running Files on LMX
(http://support.microsoft.com/kb/160807/EN-US/ )Cannot Connect to Windows NT Server with Many Shares
(http://support.microsoft.com/kb/150215/EN-US/ )Disabling Automatic Network Shortcut Resolution
(http://support.microsoft.com/kb/138014/EN-US/ )File May Be Truncated to Zero Bytes When Copied Onto Itself
(http://support.microsoft.com/kb/136834/EN-US/ )Error Copying Read-Only Files to Core SMB Server
(http://go.microsoft.com/fwlink/?LinkId=151500)for other considerations.