First, any hosting company should provide the raw IIS logs as a matter of service.  But they won't show how you got hacked, because it wasn't an IIS request.  Or DNN.  Or the Onyak modules.  Someone (or something) was able to write to the folders in youir web site.  This is typical of a scripted hack since it was in all folders, and could be due to weak FTP login controls but is more likely the result of a host-wide issue.  Possibly even another hosted account installing a trojan.  Or even you installing one, though if you only run DNN that's less likely.

Your host should be checking all hosted sites, and should be flattening the box and reinstalling with a known-good backup.  If it is only your site, they should be forcing a password change, use of strong passwords and forced rotation of passwords.  You should wipe all your content and reinstall DNN and restore from a known-good backup.

Jeff

From years of experience managing Web servers, and IIS specially, I can tell you that it is not a DNN security weakness.  This is most likely a Web server misconfiguration.  That type of attack has been going on for years by script kiddies that target a bunch of addresses to see which one they can get through.  Believe me, it is not DNN.

This type of attack for instance was done a lot to servers that had the FrontPage Web Server Extensions installed, which are not needed for DNN.  Ask if the FrontPage Web Server extensions are installed on the server you use, if they are, they were probably the culprit, it is tricky to manage the IIS security with the FP Serv Ext installed.  Also, ask them to remove them.

Carlos