# activar el inicio y la interfaz /etc/default/knockd
# config para /etc/knockd.conf (man knockd)
[options]
	UseSyslog

[opencloseSSH]
	sequence      = 4,8,15,16,23,42
	seq_timeout   = 60
	tcpflags      = syn
	start_command = /sbin/iptables -I INPUT -s %IP% -p tcp --syn --dport 22 -j ACCEPT
	cmd_timeout   = 120
	stop_command  = /sbin/iptables -D INPUT -s %IP% -p tcp --syn --dport 22 -j ACCEPT