Rule:

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Sid:
1332

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Summary:
Attempted id command access via web

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Impact:
Attempt to gain information on users and groups that exist on the host
using the id command.

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Detailed Information:
This is an attempt to gain intelligence about the users on a host. "id"
is a UNIX command that will return information about the system's users
and groups. This information is valuable to an attacker who can use it
to plan further attacks based on the users possible login information or
be more effective in targeting specific users and groups who possess
elevated privileges . The id command will return information on the
user, the groups the user belings to and the users' "gid" and "uid".

The rule looks for the "id" command in the client to web server network
traffic and does not indicate whether the command was actually
successful in showing the user information. The presence of the "id"
command web traffic indicates that an attacker attempted to trick the
web server into executing system in non-interactive mode i.e. without a
valid shell session. 

Alternatively this rule may trigger in an unencrypted HTTP tunneling
connection to the server or a shell connection via another exploit
against the web server.

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Attack Scenarios:
1. The attacker can make a standard HTTP request that contains
'/usr/bin/id' in the URI which can then return sensitive information on
groups and users present on the host. 

2. This command may also be requested on a command line should the
attacker gain access to the machine.

3. An attacker uses a "id" command via a web server connection to test
what username the web server runs under. He then looks for all the files
writable by this user and find a web server configuration file with
wrong permissions.

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Ease of Attack:
Simple HTTP request.

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False Positives:
None Known

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False Negatives:
None Known

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Corrective Action:

Webservers should not be allowed to view or execute files and binaries
outside of it's designated web root or cgi-bin. 

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Contributors:
Sourcefire Research Team
Nigel Houghton <nigel.houghton@sourcefire.com>
Additional information from Anton Chuvakin <http://www.chuvakin.org>

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Additional References:
sid: 1333

man id

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