ShieldWall embraces the zero-trust principle and instruments your server firewall to block inbound connections from every IP on any port, by default. The website allows you to push policies to your agents and temporarily unlock certain ports from your IP.
Follow the instructions here and then log into your https://shieldwall.me/ account to control the agent.
https://github.com/evilsocket/shieldwall/wiki
Released under the GPL3 license.