Tinyproxy
http://tinyproxy.github.ioOn Debian and derived distributions, run apt-get install tinyproxy to ... set up a set of rules for deciding whether an upstream proxy server is to be used, ...
Linux as a Proxy Server | Linux Journal
www.linuxjournal.com › article › 2408Dec 01, 1997 · The proxy server is used to allow Internet access from inside the protected network through either the single or dual-homed host firewall. The client applications speak directly to the proxy server and the proxy server in turn speaks directly to the Internet hosts on behalf of the client, thusacting as a proxy.