Windows 95 Update to Encrypt Passwords in Memory

ID: Q165402

The information in this article applies to:

Microsoft Windows 95
Microsoft Windows 95 OEM Service Release version 1
Microsoft Windows 95 OEM Service Release version 2
Microsoft Windows 95 OEM Service Release version 2.1

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:

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. Click the file names below to download the files:

Secupd.exe

Secupd2.exe

Nwredup4.exe

For more information about how to download files from the Microsoft Download Center, please visit the Download Center at the following Web address

http://www.microsoft.com/downloads/search.asp

and then click How to use the Microsoft Download Center. 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:

Q165403 Windows 95 Update Prevents Sending Clear-Text Password Over Net

Q161100 File May Be Truncated When Copied to a Full Network Drive

Q157114 "Access Denied" Attempting to Run File on LM/X Server

Q156497 Duplicate Print Output on PC-LAN Server from Windows 95 Client

Q152186 Possible Network Data Corruption If Locking Not Used

Q148367 Possible Network File Corruption with Redirector Caching

Q142803 Updated Vredir.vxd Corrects Problems Accessing Database Files

Q140558 Deleting Files on Samba Servers May Delete Local Files Instead

Q138249 Updated Vredir.vxd Corrects Errors Running Files on LMX

Q160807 Cannot Connect to Windows NT Server with Many Shares

Q150215 Disabling Automatic Network Shortcut Resolution

Q138014 File May Be Truncated to Zero Bytes When Copied Onto Itself

Q136834 Error Copying Read-Only Files to Core SMB Server

Nwredir.vxd:

Q163673 "Exception 0E" Using MSNDS Over Dial-Up Connection

Q160824 MSNDS Drops Connections to More Than Eight Servers

Q158058 MSNDS Client Does Not Prompt to Log On

Q153470 Incorrect Error Code Returned for Locked Files

Q152186 Possible Network Data Corruption If Locking Not Used

Q151912 NWRedir Returns Cached File Size Information

Q149606 Fatal Exception 0E in VNETBIOS Using NetWare Login Script

Q147838 Cannot Access Folders with Long File Names on NetWare Servers

Q143282 No Documents Appear in the File Open Dialog Box

Q139747 MS-DOS-Based Program Reports Not Enough NetWare Server Space

Q136303 Connecting to Schedule+ 1.0 Calendar File Drops Connections

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

Q164377 Cannot Connect to Remote Access Server with Dial-Up Networking

Q149396 Cannot Change Expired Windows NT Password with DUN

Q154434 Err Msg: No Domain Controller Was Available to Validate...

Additional query words: security

Keywords : kbfile kbnetwork win95
Version : WINDOWS:95
Platform : WINDOWS
Issue type : kbprb