denideWe’ve had Microsoft ISA Server running for a couple of weeks and ever since we upgraded to the new version we haven’t been able to write new files or delete existing files from an FTP connection.

The wierd thing is that we could make a FTP connection and download anything we wanted. We checked the permissions first because that’s what it really seemed like. However, we could make a FTP connection on a computer that wasn’t behind the ISA Server and delete to our heart’s content, so we knew it had to be something to do with the proxy server/firewall.

After some research on the web and some trial and error I finally figured it out. By default ISA Server 2004 restricts FTP traffic to read only. To change this you need to configure the FTP filter that allows the FTP traffic. For our setup the rule that allows the FTP traffic is called “Unrestricted Internet” rule, right-click and select Configure FTP. You’ll get the “Configures STP protocol policy” dialog bog and you’ll notice that the Read Only is checked. Remove the check box and hit ok. Then you’ll have to hit apply to save changes to the configuration.

After that make sure you disconnect your FTP session and reconnect since the new configuration has been applied. Once you re-connect you’ll be able to upload and delete all the files you want!