GEN:SID 1:1024
Message WEB-IIS newdsn.exe access
Summary This event is generated when an attempt is made to access the newdsn.exe file, which is a sample program installed with Internet Information Server (IIS) 3.0.
Impact File creation.  This attack can allow the creation of a new Microsoft Access Database (.mdb) file on the vulnerable server.
Detailed Information IIS 3.0 comes with a sample program newdsn.exe.  An attacker can craft a URL to reference this executable and, as a parameter, pass the name of a new file to be created.  The file may have any extension, but will be considered a Microsoft Access Database file.
Affected Systems IIS 3.0 servers
Attack Scenarios An attacker can craft a URL to execute the vulnerable newdsn.exe and create a Microsoft Access Database file on the vulnerable server.
Ease of Attack Simple.  
Corrective Action Delete the newdsn.exe file.

Upgrade to a more current version of IIS.
Additional References CVE
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-1999-0191

Rule References bugtraq: 1818
cve: 1999-0191
nessus: 10360