File: 1883.txt

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Rule:


--
Sid:

1883

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Summary: 
This rule has been placed in deleted.rules

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Impact: 

attacker might have gained an ability to execute commands remotely on the system.

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Detailed Information:

This signature triggers when a UNIX "id" command is used to confirm
the user name of the currently logged in user over any unencrypted
connection. Such connection can be either a legitimate telnet
connection or a result of spawning a shell on FTP, POP3, SMTP or other
port as a consequence of network exploit. The string "uid=" and
"(nobody)" is an output of an "id" command indicating that the user
has "nobody" account privileges, typically used by the web server
process.  Seeing such a response indicates that some user connected
over the network to a target web server and likely exploited the web
server to launch a shell.

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Attack Scenarios: 

a buffer overflow exploit against the WWW server results in "/bin/sh" being executed. An automated script performing an attack, checks for the success of the exploit via an "id" command.

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Ease of Attack: 

this post-attack behavior can accompany different attacks

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False Positives: 

the signature will trigger if a legitimate system administrator executes the "id" command over the telnet connection which uses one of the web ports, as defined in snort.conf

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False Negatives: 

not known

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Corrective Action: 

investigate the server for signs of compromise, run the integrity checking software, look for other IDS alerts involving the same IP addresses.

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Contributors: 

Anton Chuvakin <anton@chuvakin.org>

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Additional References:

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