Access Violation in DNS.EXE Caused by Malicious Telnet Attack

 Last reviewed: June 9, 1997
Article ID: Q169461
The information in this article applies to:
  • Microsoft Windows NT Server version 4.0

SYMPTOMS

You may receive an Access Violation in Dns.exe. This is most often occurs on computers connected to public networks, such as the Internet, where deliberate attacks are common.

CAUSE

This particular attack is usually generated maliciously by typing the following command on the attacking system: 

   telnet <mycomputer> 19 | telnet <mycomputer> 53
This command causes a telnet connection to be established to port 19 (the chargen service, which generates a string of characters) with the output redirected to a telnet connection to port 53 (the DNS service.) This flood of characters causes an Access Violation in the DNS service, which is terminated, disrupting name resolution services.

RESOLUTION

The Microsoft DNS Server has been modified to to correct this problem. Obtain the following fix or wait for the next Windows NT service pack.

This hotfix has been posted to the following Internet location: 

   ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/usa/NT40/
   hotfixes-postSP3/dns-fix

STATUS

Microsoft has confirmed this to be a problem in Windows NT version 4.0. A supported fix is now available, but has not been fully regression-tested and should be applied only to systems experiencing this specific problem. Unless you are severely impacted by this specific problem, Microsoft recommends that you wait for the next Service Pack that contains this fix. Contact Microsoft Technical Support for more information.

Additional reference words: 4.00 prodnt denial of service dns telnet port
53
Keywords : kbbug4.00 kbnetwork NTSrv nttcp
Version : 4.0
Platform : winnt
Issue type : kbbug
Resolution Type : kbfix

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Last reviewed: June 9, 1997
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