Windows 95 Update to Encrypt Passwords in Memory

Article translations Article translations
Article ID: 165402 - View products that this article applies to.
This article was previously published under Q165402
This article has been archived. It is offered "as is" and will no longer be updated.
Expand all | Collapse all

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.

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.

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.

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:
  1. 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.
  2. In My Computer or Windows Explorer, double-click the update file(s) you downloaded in step 1.
  3. Follow the instructions on the screen.
The following files are available for download from the Microsoft Download Center:
Collapse this imageExpand this image
DOWNLOAD
Download Secupd.exe now
Collapse this imageExpand this image
DOWNLOAD
Download Secupd2.exe now
Collapse this imageExpand this image
DOWNLOAD
Download Nwredup4.exe now
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 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.

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 Windows 95 Update Prevents Sending Clear-Text Password Over Net
161100 File May Be Truncated When Copied to a Full Network Drive
157114 "Access Denied" Attempting to Run File on LM/X Server
148367 Possible Network File Corruption with Redirector Caching
142803 Updated Vredir.vxd Corrects Problems Accessing Database Files
140558 Deleting Files on Samba Servers May Delete Local Files Instead
138249 Updated Vredir.vxd Corrects Errors Running Files on LMX
160807 Cannot Connect to Windows NT Server with Many Shares
150215 Disabling Automatic Network Shortcut Resolution
138014 File May Be Truncated to Zero Bytes When Copied Onto Itself
136834 Error Copying Read-Only Files to Core SMB Server
Rasapi32.dll/Pppmac.vxd:nect to Remote Access Server with Dial-Up
154434 Err Msg: No Domain Controller Was Available to Validate...

Properties

Article ID: 165402 - Last Review: November 3, 2013 - Revision: 4.0
Applies to
  • Microsoft Windows 95
Keywords: 
kbnosurvey kbarchive kbdownload kbfile kbgraphxlinkcritical kbnetwork kbprb KB165402

Contact us for more help

Contact us for more help
Connect with Answer Desk for expert help.
Get more support from smallbusiness.support.microsoft.com