[Snort-sigs] SID 496

Anton Chuvakin anton at ...1177...
Tue Jan 14 21:48:02 EST 2003

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RESPONSES directory listing"; content:"Directory of"; nocase;
flow:from_server,established; classtype:unknown; sid:496; rev:7;)

Sid: 496

Summary: A post-compromise behavior indicating the use of Windows command shell.


Impact: attacker might have gained an ability to execute commands remotely

Detailed Information:

The signature is aimed at catching the standard Windows commands for
listing directories. The string "Directory of" is typically shown in
front of the directory listing on Windows NT/2000/XP.  Seeing such a
response in the HTTP traffic indicates that somebody have managed to
"convince" the web server to spawn a shell bound to a web port and
have successfully executed at least one command to list the
directory. Note that the source address of this signature is actually
the victim and not the attacker as for the exploit signatures.


Attack Scenarios: an attacker gains an access to a Windows web server
via IIS vulnerability and manages to start a cmd.exe shell. He then
proceeds to look for interesting files on the compromised server via
the "dir" command.


Ease of Attack: this post-attack behavior can accompany different


False Positives: the signature will trigger if the string "Directory
of" appears in the content distributed by the web server, in which
case the signature should be tuned.

False Negatives: not known


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

Contributors: Anton Chuvakin <http://www.chuvakin.org>

Additional References:

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