A system for providing secured file transfer protocol ("FTP") services between a passive FTP client system coupled to a private network and a FTP server coupled to a public communication network, such as the Internet. The passive FTP client system requests a communication session with a first proxy server that is coupled to the private network. The passive FTP client system submits to the first proxy server the uniform resource locator ("URL") of a desired FTP server. The first proxy server initiates an outbound request from the private network, through a single port on a firewall, to a second proxy server that is coupled to the public communication network. The first proxy server submits the URL to the second proxy server. The second proxy server uses the URL to establish a FTP session with the desired FTP server. Upon receiving an identified socket provided by the FTP server for the data channel, the first proxy server changes the received data packets from the FTP server by substituting its own IP address for the FTP server's IP address, thus identifying a new socket on the first proxy server. The passive FTP client system transmits a FTP data request to the new socket on the first proxy server. The first proxy server forwards the data request to the FTP server via the outbound connection established with the second proxy server. All FTP data flows through a single port on the firewall.