-----BEGIN PGP SIGNED MESSAGE----- =========================================================================== AA-97.25 AUSCERT Advisory Windows95 Network Password Vulnerability 3 June 1997 Last Revised: -- - --------------------------------------------------------------------------- AUSCERT has received information that a vulnerability exists in the way that network passwords are stored in memory by Microsoft Windows95 systems. This vulnerability may allow the unauthorised access to the plain text password for the currently logged in user. This can lead to unauthorised access to the user's network account. Microsoft has released a security bulletin, containing patch information, addressing the vulnerability. These patches encrypt the passwords stored in memory. The security bulletin and patches are described in this advisory. - --------------------------------------------------------------------------- 1. Description A vulnerability exists in the way that network passwords are stored in memory by Microsoft Windows95 systems. This vulnerability may allow unauthorised access to the plain text password for the currently logged in user. Although the password is encrypted before sending it over a network, it is stored unencrypted in the system's memory. Access to the password for the currently logged in user is possible through careful examination of memory structures. It is possible to develop a program to simplify this attack. To obtain the password currently stored in memory, a program must be executed on the system. This can be done by either gaining physical access to the computer or misleading the user into executing the program. These actions must be performed while the network user is still logged in. The user can be misled into running a malicious program by downloading untrusted information from the Internet, or by some other means such as embedding the malicious program in a Macro contained in a file that gets executed when the file is opened by the user. This file may be sent to the user as an attachment to an electronic mail message. 2. Impact Unauthorised access may be gained to the network password of the user logged in to a Windows95 system. This can lead to unauthorised access to the user's network account using the compromised password. 3. Workarounds/Solution Official vendor patches have been released by Microsoft which address this vulnerability (Section 3.1). AUSCERT recommends that sites apply the patches given in this bulletin immediately. 3.1 Install vendor patches Microsoft has released a security bulletin, containing patch information, addressing the vulnerability described in this advisory. This bulletin can be located on their security page on Microsoft's Web site at http://www.microsoft.com/security/ and is titled "Microsoft Windows 95 Update to Enhance Password Security". Additionally, a Microsoft Knowledge Base article has been developed by Microsoft detailing more information about this problem and associated fixes. It can be located by going to Microsoft Australia's home page (http://www.microsoft.com.au) and following the links to "Support", and then to "Knowledge Base". The specific Knowledge Base article to search for is Q165402. This article can also be referenced as http://www.microsoft.com/kb/articles/q165/4/02.htm Both the bulletin and the Knowledge Base article contain pointers to patches that can be downloaded. AUSCERT recommends that sites apply the patches given in this bulletin immediately. 4. Additional Measures To gain access to the user's password, the user must first be logged in to the network from a Windows95 system using their account and password. The password is obtained by either someone running a program on the system, or a program must be executed by the user or on the user's behalf. Executing a program can be done by either gaining physical access to the system or misleading the user into running an untrusted program. The user can be misled into running a malicious program by downloading untrusted information from the Internet, or by some other means such as embedding the malicious program in a Macro contained in a file that gets executed when the file is opened by the user. This file may be sent to the user as an attachment to an electronic mail message. Educating users can address each of these scenarios. The ability to exploit this vulnerability can be reduced if unauthorised access to the system, while the user is still logged in, can be minimised or eliminated. One way this can be achieved is if each user logs off from the network any time they leave the computer for reasonable periods of time, or runs a password protected screen saver. Users should also be educated not to run untrusted programs that have been given to them on disk or via Email, or downloaded from a network. Email attachments should be scanned for any unauthorised macros. - --------------------------------------------------------------------------- AUSCERT thanks the Australian Bureau of Statistics and Microsoft for their assistance and response in the preparation of this Advisory. - --------------------------------------------------------------------------- The AUSCERT team have made every effort to ensure that the information contained in this document is accurate. However, the decision to use the information described is the responsibility of each user or organisation. The appropriateness of this document for an organisation or individual system should be considered before application in conjunction with local policies and procedures. AUSCERT takes no responsibility for the consequences of applying the contents of this document. If you believe that your system has been compromised, contact AUSCERT or your representative in FIRST (Forum of Incident Response and Security Teams). AUSCERT is located at The University of Queensland within the Prentice Centre. AUSCERT is a full member of the Forum of Incident Response and Security Teams (FIRST). AUSCERT maintains an anonymous FTP service which is found on: ftp://ftp.auscert.org.au/pub/. This archive contains past SERT and AUSCERT Advisories, and other computer security information. AUSCERT also maintains a World Wide Web service which is found on: http://www.auscert.org.au/. Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 4477 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AUSCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). On call after hours for emergencies. Postal: Australian Computer Emergency Response Team Prentice Centre Brisbane Qld. 4072. AUSTRALIA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Revision History ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -----BEGIN PGP SIGNATURE----- Version: 2.6.3i Charset: noconv Comment: ftp://ftp.auscert.org.au/pub/auscert/AUSCERT_PGP.key iQCVAwUBM5PWMyh9+71yA2DNAQHCuAP7BWLww8EpTjAdKlZjuRsnykeiGwZwaof3 GRnvsc5i2BnQ/uYBTqOAds5MaajN4GHQXMUY0hIPvPjHsGc26GD9CwHsLrEONXBD zjwG5acwFW6S4REWZcqMkvISIZzOlvbhYdV3pmPpDDSf7Hv1FpsH0zQu2aaDmo5W KYmabfKHXGw= =iiO8 -----END PGP SIGNATURE-----