Rule:   

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Sid: 322

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Summary: 
This event is genrated when an attempt is made to query the finger daemon to ascertain a list of usernames on a system.

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Impact: 
Information gatthering, the attacker may obtain the list of some accounts existing on the victim system as a prelude to further compromize.

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Detailed Information:
This event is generated when an attempt to use a search feature in "cfingerd" version of a finger daemon is attempted. The search feature allows the attacker to obtain the lists of accounts existing on the target system by issuing a specially crafted finger request to "search" for information. Knowing the list of accounts might facilitate a password guessing attacks, email attacks or other abuse.

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Attack Scenarios:
An attacker learns that "guest" account exists and has never been used. He then guesses that the password for this account and logs in to the system remotely using telnet.

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Ease of Attack: 
Simple, no exploit software required

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False Positives:
None Known

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False Negatives: 
None Known

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Corrective Action: 
Look for other IDS events involving the same IP addresses. 

Look for suspicious logins to the affected system.

Disable the finger daemon or apply a vendor patch that removes the vulnerability

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Contributors: 
Original rule writer Max Vision <vision@whitehats.com>
Snort documentation contributed by Anton Chuvakin <http://www.chuvakin.org>
Sourcefire Vulnerability Research Team
Nigel Houghton <nigel.houghton@sourcefire.com>

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Additional References:

OSVDB:
http://www.osvdb.org/32

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