full-disclosure - smtpsvc and undocumented registry values

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From: thierry.haven at xmcopartners.com (Thierry Haven)
Subject: smtpsvc and undocumented registry values

Hi,
I?ve been hacking around smtpsvc.dll (Windows Server 2003) in order to hide the Server version when a mail is relayed:

Original header:
"from [192.168.X.X] ([192.168.X.X]) by winserv2003 with Microsoft SMTPSVC(6.0.3790.0);	 Wed, 23 Feb 2005 15:47:51 +0100" 

I found that it is possible to remove this information by patching the code directly in the DLL:

Modified header:
"from [192.168.X.X] ([192.168.X.X]) by winserv2003 with some server;	 Wed, 23 Feb 2005 15:49:51 +0100" 

... Assuming that smtpsvc.dll checks its own version at runtime by retrieving information in the .rsrc section of the PE thanks to version.dll calls. However I'd like to know if there is a better way to disable this "feature" (maybe a key in the registry ?). 

Next I'd like to ask about such undocumented registry values. Where to find information about them ?

Best Regards,

_______________________________________
Thierry Haven - Xmco Partners
Security Consulting / Pentest
web  : http://www.xmcopartners.com