Denial of Service Attack Against WinNT Simple TCP/IP Services (154460)
The information in this article applies to:
- Microsoft Windows NT Server 4.0 Terminal Server Edition
- Microsoft Windows NT Workstation 4.0
- Microsoft Windows NT Server 4.0
This article was previously published under Q154460 SYMPTOMS
As your computer is being attacked there may be a jump in bandwidth
utilization on a subnet containing Windows NT computers and performance may
suffer. A network analyzer shows a large amount of UDP traffic, typically
from port 19 (chargen).
CAUSE
A malicious attack may be mounted against Windows NT computers with the
Simple TCP/IP Services installed. The attack consists of a flood of UDP
datagrams sent to the subnet broadcast address with the destination port
set to 19 and a spoofed source IP address. The Windows NT computers running
Simple TCP/IP services respond to each broadcast, creating a flood of UDP
datagrams.
RESOLUTION
Windows NT TCP/IP, Windows Sockets, and Simple TCP/IP services have been
modified to be more attack resistant. Windows Sockets now supports a new
socket option, SO_BROADCAST, that can be set to allow the recvfrom() call
to pass broadcast datagrams to the application. The default for this option
is OFF. Previous implementations passed broadcasts datagrams to any Windows
Sockets application that issued a recvfrom() call. Additionally, the
chargen service and other Simple TCP/IP services have been modified to drop
any datagrams that have the source port equal to the destination port to
prevent "looping" attacks.
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 the
Microsoft 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 been
posted to the following Internet location. However, Microsoft recommends
that you install Windows NT 4.0 Service Pack 4 to correct this problem.
ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/usa/nt40/
hotfixes-postSP3/simptcp-fix
NOTE: An updated version of this hotfix was posted on August 15, 1997.
STATUS
Microsoft has confirmed this problem could result in some degree of
security 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.
| Modification Type: | Major | Last Reviewed: | 6/24/2004 |
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| Keywords: | kbbug kbfile kbfix kbnetwork KB154460 |
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