Q185378: IIS 4.0: FTP "Bounce" Attack and CERT Advisory CA-97.27

Article: Q185378
Product(s): Internet Information Server
Version(s): winnt:4.0
Operating System(s): 
Keyword(s): 
Last Modified: 14-JUL-2000

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Internet Information Server 4.0 
-------------------------------------------------------------------------------

SUMMARY
=======

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:

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

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1986-2002.