FTP with SSL connection (WS FTP pro / IIS 5) "500 'AUTH SSL': command not understood"

Posted on 2004-10-09
Medium Priority
Last Modified: 2013-12-04
Issue: WS FTP Pro cannot establish FTP with SSL connection. 500 'AUTH SSL': command not understood


 Server: IIS 5 on Windows 2000 Server (latest Updates from MS), Thawte Certificate Installed
 Client: WS FTP Pro 9.01 Client for Windows (98,2000,XP,2003...)


 Regular FTP connection can be established with proper USERID/PASSWORD.
 "FTP with SSL" connection doesn't succeed; give following error:
Finding Host ftp.starrfish-xyz.com...
Connecting to
Connected to in 0.015625 seconds, Waiting for Server Response
Initializing SSL Session ...
220 starfish Microsoft FTP Service (Version 5.0).
500 'AUTH SSL': command not understood

Any suggestion regarding problem/ solution will be greatly appreciated.


Question by:tjipro
  • 2
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LVL 34

Expert Comment

ID: 12267701
The Microsoft FTP service does not support SSL in any of its versions to date.

If you want to use SSL secured FTP you will need to move to a different FTP server product.


Dave Dietz


Author Comment

ID: 12272687
Dave, this is interesting. Is it possible to use IIS web server for FTP with SSL by using any interface that you know of?

LVL 34

Accepted Solution

Dave_Dietz earned 500 total points
ID: 12273548
If you are looking for secure file transfers the only native way to do this in IIS is via WebDAV.

Do a search on WebDAV in the IIS Help files and you should find enough to get you started.

If you are tied to FTP for some reason you could use an SSL proxy for FTP.  There are some free and some commercial SSL proxies that can be used for secure FTP.  The general idea is that you create an SSL connection to the proxy (often installed on the same machine) which then makes an unsecure connection to the FTP server (since this happens internally the traffic is not vulnerable to sniffing on the Internet).

A couple samples on the web (I have not tested/used these go I make no guarantees):


Dave Dietz

Author Comment

ID: 12278069
Dave, Thanks for this useful information.


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