Microsoft Discovers, Fixes Security Breaches
- By Scott Bekker
- December 17, 1999
Two security vulnerabilities - one in Syskey, a utility that provides additional protection for Windows NT databases and one in Windows NT that could allow a malicious user to cause an NT machine to stop responding to requests for service - were discovered by Microsoft and have been remedied by a single patch.
Syskey is a utility that encrypts the hashed password in the SAM database in order to protect it against offline password cracking attacks. However, Syskey reuses the keystream used to perform some of the encryption. This significantly reduces the strength of the protection it provides by enabling a well-known cryptanalytic attack to be used against it.
The Windows NT Local Security Authority (LSA) provides a number of functions for enumerating and manipulating security information. One of these functions, LsaLookupSids(), is used to determine the Security Identifier (SID) associated with a particular user or group name. A flaw in the implementation of this function causes it to incorrectly handle certain types of invalid arguments. If an affected call were made to this function, it would cause the LSA to crash, thereby preventing the machine from performing useful work.
Both vulnerabilities affect Windows NT Workstation 4.0, Server 4.0, Server 4.0 Enterprise Edition, and Server 4.0 Terminal Server Edition. The patch remedies both vulnerabilities and is available in x86 version at http://www.microsoft.com/Downloads/Release.asp?ReleaseID=16798 and in Alpha version at http://www.microsoft.com/Downloads/Release.asp?ReleaseID=16799. -- Isaac Slepner
Scott Bekker is editor in chief of Redmond Channel Partner magazine.