[Snort-sigs] SID 1360
anton at ...1177...
Thu Apr 17 15:19:09 EDT 2003
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# $Id: snort-sid-1334.txt,v 1.1 2003/02/18 22:31:30 anton Exp anton $
Rule: alert tcp $EXTERNAL_NET any -> $HTTP_SERVERS $HTTP_PORTS
(msg:"WEB-ATTACKS netcat command attempt"; flow:to_server,established;
content:"nc%20";nocase; sid:1360; classtype:web-application-attack;
Summary: A web command execution attack involving the use of a
Impact: attacker might have gained an ability to execute system commands
remotely on the system
Detailed Information: This signature triggers when a "netcat"
command is used over a plain-text (unencrypted) connection on one of
the specified web ports to the target web server. The "netcat" command
may be used establish an interactive shell session to the machine and
also transfer files over the connection. The signature looks for the
"netcat" command in the client to web server network traffic and does
not indicate whether the command was actually successful. The presence
of the "netcat" command in the URL indicates that an attacker
attempted to trick the web server into executing system in
non-interactive mode i.e. without a valid shell session. Another case
when this signature might trigger is unencrypted HTTP tunneling
connection to the server or a shell connection through an exploit of
the web server.
Attack Scenarios: An attacker uses a "netcat" command to
move his rootkit to the system.
Ease of Attack: very easy, no exploit software required
False Positives: any sting containing 'nc' followed by space in the
URL will trigger the alarm.
False Negatives: none known
Corrective Action: check the web server software for vulnerabilities
and possible upgrade the system to the latest version, also
investigate the server for signs of compromise
Contributors: Anton Chuvakin <http://www.chuvakin.org>
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