This article was previously published under Q169461
This article has been archived. It is offered "as is" and will no longer be updated.
You may receive an Access Violation in Dns.exe. This is most often occurson computers connected to public networks, such as the Internet, wheredeliberate attacks are common.
This particular attack is usually generated maliciously by typing thefollowing command on the attacking system:
telnet <mycomputer> 19 | telnet <mycomputer> 53
This command causes a telnet connection to be established to port 19 (thechargen service, which generates a string of characters) with the outputredirected to a telnet connection to port 53 (the DNS service.) This floodof characters causes an Access Violation in the DNS service, which isterminated, disrupting name resolution services.
The Microsoft DNS Server has been modified to correct this problem.
To resolve this problem, obtain the latest service pack for Windows NT 4.0 or Windows NT Server 4.0, Terminal Server Edition. For additional information, click the following article number to view the article in theMicrosoft Knowledge Base:
152734 How to Obtain the Latest Windows NT 4.0 Service Pack
For your convenience, the English version of this post-SP3 hotfix has beenposted to the following Internet location. However, Microsoft recommendsthat you install Windows NT 4.0 Service Pack 4 to correct this problem.
For additional information, please see the following article(s) in theMicrosoft Knowledge Base:
162927 Telnetting to Port 53 May Crash DNS Service
Microsoft has confirmed this problem could result in some degree ofsecurity vulnerability in Windows NT version 4.0. This problem was first corrected in Windows NT 4.0 Service Pack 4.0 and Windows NT Server 4.0, Terminal Server Edition Service Pack 4.