ffproxy -- Fast Filtering Proxy, is a filtering HTTP/HTTPS proxy server.
It's capable of filtering by host, URL, and header.  Custom header
entries can be created for filtering. It can also drop privileges and
optionally chroot(8) to a chosen directory. Logging to syslog(3) is
supported, as is using another auxiliary proxy server. An HTTP accelerator
feature (acting as a front-end to an HTTP server) is also included.
Contacting IPv6 servers as well as binding to IPv6 is supported which
allows transparent IPv6 over IPv4 browsing (and vice versa).