[Snort-sigs] SID 325

Anton Chuvakin anton at ...1177...
Thu Jan 30 20:33:03 EST 2003

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alert tcp $EXTERNAL_NET any -> $HOME_NET 79 (msg:"FINGER probe 0
attempt"; flow:to_server,established;
content:"0";reference:arachnids,378; classtype:attempted-recon;
sid:325; rev:3;)

Sid: 325


Summary: An intelligence gathering attack against the finger daemon


Impact: attacker will obtain the list of some accounts existing on the
victim system

Detailed Information:

The signature is triggerred when an attempt to use a finger command
against a UNIX host with a username of "0" is launched.  Such finger query
against the vulnerable finger daemon allows the attacker to obtain a list
of some accounts existing on the target system with some details on each
account (such as time and source of the last login). Knowing the list of
accounts might facilitate a password guessing attacks, email attacks and
other abuse.


Attack Scenarios: an attacker learns that "sys" account exists on the
system. He then proceeds to guess the password remotely and connects to
the system.


Ease of Attack: very easy, no exploit software required


False Positives: not known

False Negatives: not known


Corrective Action: disable fingerd daemon 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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