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Article ID: 165402 - Last Review: November 15, 2006 - Revision: 3.1

Windows 95 Update to Encrypt Passwords in Memory

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This article was previously published under Q165402

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SYMPTOMS

If a computer running Windows 95 is left unattended while a user is logged on to a network, it may be possible to obtain that user's network password by a programmatic examination of the computer's memory. Typically, accomplishing this would require physical access to the computer. However, the network password could also potentially be acquired if a program designed to search for passwords using the same examination of memory were to be downloaded and run by a currently logged-on user.

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CAUSE

In Windows 95, passwords are encrypted before being sent over the network. However, the network password for the user who is currently logged on to the Windows 95-based computer is stored temporarily in memory in an unencrypted format.

Using detailed knowledge of Windows 95 internal memory structures, it may be possible to write a program that runs in Windows 95 and reads the password for the currently logged-on user from memory.

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RESOLUTION

Microsoft recommends the following precautions to prevent the current user's network password from being accessed by unauthorized means:

Log off the computer when you leave it for long periods of time.
Run a password-protected screen saver when you leave the computer for short periods of time.
Do not run untrusted programs on the network, the Web, or that have been sent in e-mail.
Install the update described in this article.

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STATUS

Microsoft has confirmed this to be a problem in Microsoft Windows 95 and OEM Service Release 2 (OSR2). An update to address this problem is now available.

This issue is resolved by the following updated files:

For Windows 95 (all releases):
Mprserv.dll version 4.00.955 (dated 6/12/97) and later
Nwnet32.dll version 4.00.951 (dated 4/21/97) and later
Nwredir.vxd version 4.00.960 (dated 4/21/97) and later
Pppmac.vxd version 4.00.954 (dated 4/28/97) and later
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 Windows 95 (retail release) and OEM Service Release 1 (OSR1) only:
Rasapi32.dll version 4.00.954 (dated 4/25/97) and later
For Windows 95 OSR2 and OSR2.1 only:
Rasapi32.dll version 4.00.1113 (dated 4/25/97) and later
For the Microsoft Service for NetWare Directory Services [MSNDS] (all Windows 95 releases):
Nwredir.vxd version 4.00.975 (dated 4/21/97) and later

To install this update, follow these steps:

Download the appropriate update file(s) to an empty folder.
1. If you are running Windows 95 retail release (version 4.00.950) or OSR1 (version 4.00.950 A), download the Secupd.exe file.
2. If you are running Windows 95 OEM Service Release 2 or 2.1 (version 4.00.950 B), download the Secupd2.exe file.
3. If you are running the Microsoft Client for NetWare Networks with the Microsoft Service for NetWare Directory Services (MSNDS) installed, also download the Nwredup4.exe file.
In My Computer or Windows Explorer, double-click the update file(s) you downloaded in step 1.
Follow the instructions on the screen.

The following files are available for download from the Microsoft Download Center:

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Download Secupd.exe now (http://download.microsoft.com/download/win95upg/osr1/1/w95/en-us/secupd.exe)

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Download Secupd2.exe now (http://download.microsoft.com/download/win95upg/secure/1/w95/en-us/secupd2.exe)

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Download Nwredup4.exe now (http://download.microsoft.com/download/win95upg/updt_l/1.0/w95/en-us/nwredup4.exe)

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 (http://support.microsoft.com/kb/119591/EN-US/ ) How to Obtain Microsoft Support Files from Online Services

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.

This problem was corrected in Microsoft Windows 98.

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MORE INFORMATION

These components have been updated to encrypt the current user's network password even when it is stored in memory so that it cannot be read even by a programmer with detailed knowledge of Windows 95 internal memory structures.

For additional information about Windows 95 security, see Chapter 14 ("Security") in the Windows 95 Resource Kit.

The following files are installed by Secupd.exe:

   File name     Version    Date/Time        Size     Destination folder
   ---------------------------------------------------------------------
   Mprserv.dll   4.00.955   6/12/97  9:54a   127,488  Windows\System
   Nwnet32.dll   4.00.951   4/21/97  9:51a    22,016  Windows\System
   Nwredir.vxd   4.00.960   4/21/97 10:00a   123,987  Windows\System
   Pppmac.vxd    4.00.954   4/28/97  9:54a   135,288  Windows\System
   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
   Rasapi32.dll  4.00.954   4/25/97  9:54a   151,552  Windows\System

The following files are installed by Secupd2.exe:

   File name     Version    Date/Time        Size     Destination folder
   ---------------------------------------------------------------------
   Mprserv.dll   4.00.955   6/12/97  9:54a   127,488  Windows\System
   Nwnet32.dll   4.00.951   4/21/97  9:51a    22,016  Windows\System
   Nwredir.vxd   4.00.960   4/21/97 10:00a   123,987  Windows\System
   Pppmac.vxd    4.00.954   4/28/97  9:54a   135,288  Windows\System
   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
   Rasapi32.dll  4.00.1113  4/25/97 11:13a   175,104  Windows\System

The following files are installed by Nwredup4.exe:

   File name     Version    Date/Time        Size     Destination folder
   ---------------------------------------------------------------------
   Nwredir.vxd   4.00.975   4/21/97 10:15a   178,714  Windows\System

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

Vredir.vxd:

165403 (http://support.microsoft.com/kb/165403/EN-US/ ) Windows 95 Update Prevents Sending Clear-Text Password Over Net

161100 (http://support.microsoft.com/kb/161100/EN-US/ ) File May Be Truncated When Copied to a Full Network Drive

157114 (http://support.microsoft.com/kb/157114/EN-US/ ) "Access Denied" Attempting to Run File on LM/X Server

148367 (http://support.microsoft.com/kb/148367/EN-US/ ) Possible Network File Corruption with Redirector Caching

142803 (http://support.microsoft.com/kb/142803/EN-US/ ) Updated Vredir.vxd Corrects Problems Accessing Database Files

140558 (http://support.microsoft.com/kb/140558/EN-US/ ) Deleting Files on Samba Servers May Delete Local Files Instead

138249 (http://support.microsoft.com/kb/138249/EN-US/ ) Updated Vredir.vxd Corrects Errors Running Files on LMX

160807 (http://support.microsoft.com/kb/160807/EN-US/ ) Cannot Connect to Windows NT Server with Many Shares

150215 (http://support.microsoft.com/kb/150215/EN-US/ ) Disabling Automatic Network Shortcut Resolution

138014 (http://support.microsoft.com/kb/138014/EN-US/ ) File May Be Truncated to Zero Bytes When Copied Onto Itself

136834 (http://support.microsoft.com/kb/136834/EN-US/ ) Error Copying Read-Only Files to Core SMB Server

Rasapi32.dll/Pppmac.vxd:nect to Remote Access Server with Dial-Up

154434 (http://support.microsoft.com/kb/154434/EN-US/ ) Err Msg: No Domain Controller Was Available to Validate...

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APPLIES TO

Microsoft Windows 95

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Retired KB Content Disclaimer

This article was written about products for which Microsoft no longer offers support. Therefore, this article is offered "as is" and will no longer be updated.

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