[Snort-sigs] SID 329

Anton Chuvakin anton at ...1177...
Wed Feb 12 20:26:02 EST 2003


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Rule:

alert tcp $EXTERNAL_NET any -> $HOME_NET 79 (msg:"FINGER cybercop
redirection"; flow:to_server,established; content: "@localhost|0A|";
dsize:11; reference:arachnids,11; classtype:attempted-recon; sid:329;
rev:6;)

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Sid: 329

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Summary: A connection laundering attack against the finger daemon

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Impact: attacker will obtain information about a third party without a
direct connection to it

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Detailed Information:

The signature is triggerred when an attempt to use a machine to run
finger queries against the third party UNIX system is attempted by the
Cybercop vulnerability scanner.  The attack utilizes "finger
forwarding" functionality, normally used to forward queries to a third
party machine. The information is obtained without a direct connection
to the said third party, since the target systems performs a
connection for the attacker. Finger daemon is used to provide
information about the UNIX system users. It used to be installed and
enabled by default on most UNIX/Linux systems. The attack will confirm
that the target host will indeed try to forward queries.

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Attack Scenarios: a target machine is being tested for finger
weaknesses by a Cybercop vulnerability scanner

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Ease of Attack: very simple, performed by a scanner

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False Positives: not known

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False Negatives: not known

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Corrective Action: disable fingerd daemon or upgrade to a daemon with
no finger forwarding functionality


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Contributors: Anton Chuvakin <http://www.chuvakin.org>

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Additional References:

http://www.whitehats.com/info/IDS11
http://www.iss.net/security_center/advice/Intrusions/2001102/default.htm






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