# insmod ip_masq_ftp
Your Linux machine maybe uses passive mode by default, but in windows it is default to active. Even though you set INPUT, OUTPUT and FORWORD to accept by default, the gateway still have no idea what the connection from the server is for. So you still need ftp proxy. Or, use passive ftp. To change the mode to passive in windows' ftp client, type the following at the ftp prompt:
Note that if you use passive mode, there's no need for ftp proxy, that is for active ftp only. Also, set the policy to accept by default is not a good security measure, unless you are just playing with it.
Like the previous poster said, you need to take a good look at Linux Document Project (http://www.linuxdoc.org).