Frox is an FTP proxy that works transparently.
One of Frox's standout features is its support for caching FTP downloads. This can be done either by redirecting through a Squid proxy or through the proxy's own local cache. Additionally, downloads can be scanned for viruses transparently by an external scanner.
Frox's flexibility is extended even further with an interface for scripts that can be used to modify its behavior or add new features. Examples of these scripts include one that limits download file size and another that directs connections to specific hosts to mirror servers.
Security is a top priority with Frox, and the default setup runs the proxy as a non-root user in a chroot jail.
Recent updates have brought some welcomed improvements, such as logging IP addresses when name resolution fails, adding a ForceHTTP option to force downloads to go via an HTTP proxy, and closing all file descriptors before running the virus scanner to prevent the proxy from waiting forever for the scanner to exit.
Compile time options have also been added to alter Frox's argv[] so ps will give more detailed information about what each process is doing. SSL logging and documentation have also been improved, and a fix for incorrect parsing of Deny ACLs that was introduced in 0.7.16 has been implemented.
All in all, Frox should definitely be considered as a sturdy option for those in need of a versatile FTP proxy.
Version 0.7.17: N/A