GEN:SID 1:2393
Message WEB-PHP /_admin access
Summary This event is generated when an attempt is made to access the /_admin directory.
Impact Unauthorized file upload or information gathering.  This can allow an attacker to upload unauthorized files to the web server or information disclosure.
Detailed Information A vulnerability exists in the jbrowser web-based image gallery software that allows unchecked access to the _admin directory, possibly permitting an attacker to execute scripts found in this directory.  Execution of admin scripts upload.php3 and upload_ftp.php3 may allow the attacker to upload malicious files to the server or replace existing files.  Execution of the list_all.php script may allow an attacker to display files in directories, including those not in the web server root directory.
Affected Systems Not reported.
Attack Scenarios An attacker can craft a URL to execute the upload.php3, upload_ftp.php3, and list_all.php scripts to upload files or examine files on the vulnerable server.
Ease of Attack Simple.
Corrective Action Restrict access to the '_admin' directory to authorized users only.
Additional References bugtraq
http://www.securityfocus.com/bid/9537

nessus:
http://cgi.nessus.org/plugins/dump.php3?id=12032
Rule References bugtraq: 9537
nessus: 12032