Rule:

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Sid:
2042

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Summary:
This event is generated when a successful attempt has been made to login
using XTACACS from a machine outside the local area network.

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Impact:
This may be an attempt to access resources controlled by the XTACACS 
server. Data compromize may occur.

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Detailed Information:
The Extended Terminal Access Controller Access Control System (XTACACS) 
is an authentication and authorization protocol derived from  CISCO 
TACACS. It is used in tcp/ip networks where network servers authenticate
clients from a master server.

When a user logs in to a server that uses XTACACS the server then makes 
a request to a master server to detrmine the validity of the request. 
The master server then verifies the login attempt and returns data 
concerning that user which may include information regarding resources 
the user is allowed access to in the form of an access list.

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Affected Systems:
All servers using XTACACS for authentication control.

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Attack Scenarios:
Regular user login method.

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Ease of Attack:
Simple

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False Positives:

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False Negatives:
None Known

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Corrective Action:
XTACACS servers should only authenticate to known hosts and firewall 
rules should prevent access to XTACACS enabled servers from outside the 
local area network.

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Contributors:
Sourcefire Research Team
Brian Caswell <bmc@sourcefire.com>
Nigel Houghton <nigel.houghton@sourcefire.com>

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Additional References:

Network Information Library - Intel:
http://www.intel.com/support/si/library/bi0414.htm

The Internet Next Generation Project:
http://ing.ctit.utwente.nl/WU5/D5.1/Technology/xtacacs/

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