https://www.invata-online.ro/courses/linuxs/video/iptables_help/iptables_help.html
https://www.invata-online.ro/courses/linuxs/video/stateful/stateful.html
https://www.invata-online.ro/courses/linuxs/video/fara_ssh/fara_ssh.html
https://www.invata-online.ro/courses/linuxs/video/log_ping/log_ping.html