This document describes a stealth method to externally open ports that, by default, are kept closed by the firewall. Server side 1. Install knockd [codesyntax lang=”bash”] apt-get install knockd [/codesyntax] 2. Configure knockd [codesyntax lang=”bash”] vim /etc/knockd.conf [options] UseSyslog [OpenClosePort] sequence = 2123:udp,3543:tcp,6454:udp seq_timeout = 5 Start_Command = /sbin/iptables -I INPUT -s %IP% -p tcp … Continue reading Set port knocking with knockd and iptables →