FtpProxy is a module built for parsing commands of the Control Channel in the FTP protocol. It reads the REQUEST at the client side, parses it and - if the local security policy permits - sends it to the server. The proxy parses the arriving RESPONSES and sends them to the client if the policy permits that. FtpProxy uses a PlugProxy to transfer the data arriving in the Data Channel. The proxy is capable of manipulating commands and stacking further proxies (for example, MimeProxy) into the Data Channel. Both transparent and non-transparent modes are supported.

The default low-level proxy implementation (AbstractFtpProxy) denies all requests by default. Different commands and/or responses can be enabled by using one of the several predefined proxy classes which are suitable for most tasks. Alternatively, use of the commands can be permitted individually using different attributes. This is detailed in the following two sections.