Rule: 

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Sid:
332

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Summary: 
An intelligence gathering attack against the finger daemon

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Impact:
The attacker may obtain information about user accounts on the target system.

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Detailed Information:
This event is generated when an attempt is made to use a finger command against a host with a username of "0".  A finger query against a vulnerable finger daemon may allow the attacker to obtain a list of accounts on the target system with some details for each account where present (such as time and source of the last login). 

Obtaining a list of accounts might precipitate further attacks such as password guessing, email attacks and other abuse.

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Attack Scenarios:
An attacker learns that the "sys" account exists on the system. He then proceeds to guess the password and is then able to gain remote access to the system.

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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: 
Disable the finger daemon or limit the addresses that can access the service via firewall or TCP wrappers.

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

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Additional References:

CVE:
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-1999-0197

Nessus:
http://cgi.nessus.org/plugins/dump.php3?id=10069%20(Finger%20zero%20at%20host

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