Would you like to hide a port until a certain knock-knock procedure is received?
Like this:
knock3000 4000 5000 && ssh -puser@host && knock5000 4000 3000
Knock on ports to open a port to a service (ssh for example) and knock again to close the port.
First you need to install knockd.
See example config file below.
[options]
logfile = /var/log/knockd.log
[openSSH]
sequence = 3000,4000,5000
seq_timeout = 5
command = /sbin/iptables -A INPUT -i eth0 -s %IP% -p tcp –dport 22 -j ACCEPT
tcpflags = syn
[closeSSH]
sequence = 5000,4000,3000
seq_timeout = 5
command = /sbin/iptables -D INPUT -i eth0 -s %IP% -p tcp –dport 22 -j ACCEPT
tcpflags = syn
Hope you found it userful.
