# $Id: 1885.txt,v 1.1 2003/02/15 02:45:26 cazz Exp $

Rule:

alert tcp $HTTP_SERVERS $HTTP_PORTS -> $EXTERNAL_NET any (msg:"ATTACK RESPONSES id check returned http"; flow:from_server,established; content:"uid="; content:"(http)"; classtype:bad-unknown; sid:1885; rev:2;)

--
Sid: 

1885

-- 
Summary: 

A post-compromise behavior indicating the use of a UNIX "id"
command

-- 
Impact: 

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

--
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
"(http)" is an output of an "id" command indicating that the user
has "http" 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.

--
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.

-- 
Ease of Attack: 

this post-attack behavior can accompany different attacks

-- 
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

--
False Negatives: not known

-- 
Corrective Action:

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

--
Contributors: Anton Chuvakin <anton@chuvakin.org>

-- 
Additional References:
