[Snort-sigs] SID 328

Anton Chuvakin anton at ...1177...
Thu Jan 30 20:40:01 EST 2003

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alert tcp $EXTERNAL_NET any -> $HOME_NET 79 (msg:"FINGER bomb
attempt"; flow:to_server,established; content:"@@";
reference:arachnids,381; reference:cve,CAN-1999-0106;
classtype:attempted-dos; sid:328; rev:5;)

Sid: 328


Summary: A Denial-of-Service attack against a finger daemon


Impact: attacker will overload the target machine or crash the finger daemon

Detailed Information:

The signature is triggerred when a specifially crafted finger query is
directed at a target UNIX machine. 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 crash or
overload the vulnerable machines by causing the finger daemon to go into a
loop. The attack abuses the buggy "finger forwarding"  functionality,
normally used to forward queries to a third partuy machine (a security
risk in itself).


Attack Scenarios: an attacker runs an attack and slows the machine


Ease of Attack: very simple, no exploit software is required, just a
specially formatted finger query


False Positives: not known

False Negatives: not known


Corrective Action: disable fingerd daemon, patch it or limit the addresses
that can access the service via firewall or TCP wrappers.

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

Additional References:


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