DOCUMENT:Q185378  14-JUL-2000  [iis]
TITLE   :IIS 4.0: FTP "Bounce" Attack and CERT Advisory CA-97.27
PRODUCT :Internet Information Server
PROD/VER:winnt:4.0
OPER/SYS:
KEYWORDS:

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The information in this article applies to:

 - Microsoft Internet Information Server 4.0 
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SUMMARY
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The CERT (http://www.Cert.org) Advisory CA-97.27 warns of an FTP security attack
called the "Bounce" attack. This involves misuse of the Port command to
maliciously open a connection to a port on the File Transfer Protocol (FTP)
server.

The FTP Server service in Microsoft Internet Information Server version 4.0 (IIS)
is not susceptible to this attack.

MORE INFORMATION
================

The FTP server in IIS 4.0 disallows third-party data transfers. This is done via
a modification to the implementation of the Port command. When the FTP server
receives a Port command, the specified IP address must match the client's source
IP address for the control channel.

The FTP server in IIS 4.0 also has another level of protection: disallowing the
Port command from specifying reserved ports (those less than 1024) except Port
20 (the default data port). By default, any client attempt to issue a Port
command with (port < 1024 and port != 20) causes the Port command to fail.


Additional query words:

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Keywords          :  
Technology        : kbiisSearch kbiis400
Version           : winnt:4.0
Issue type        : kbinfo

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