Consider a scenario where you have a client workstation behind Forefront TMG 2010 and you are trying to download files from a FTP Server. You are successfully able to logon on the FTP but after type the command “dir” you get the error message below:
The message is pretty clear about what is going on, isn’t it? Well, it is but where do I enable this option? I don’t remember having this on ISA!! To address this issue you just need to enable a new option that we have on TMG, this option is located on the FTP Filter properties as shown below:
After enabling this option and apply the changes you should be able to list your files just fine. It is important to mention that this setting has nothing to do with the FTP Read Only option, that you had in ISA 2004/2006 and still have it on TMG. The FTP Filter when running in read only mode (see figure below) will blocks all commands in the control channel except the following ones:
“ABOR, ACCT, CDUP, CWD /0, FEAT, HELP, LANG, LIST, MODE, NLST, NOOP, PASS, PASV, PORT, PWD /0, QUIT, REIN, REST, RETR, SITE, STRU, SYST, TYPE, USER, XDUP, XCWD, XPWD, SMNT”
You can customize this list by using the sample script below (from Configuring Add-ins MSDN article),in this example the script configures FTP Access Filter to allow only the USER and PASS commands:
Note: don’t change the default Read Only commands unless you have a real business need for that.