IP traffic over ICMP tunneling
Not the first of its kind, just look-up in Wikipedia: https://en.wikipedia.org/wiki/ICMP_tunnelAny captive portal these days block also ICMP.Most firewalls block ICMP these days, because the days of blacklisting are over and ICMP is not the one who is getting white listed. Why?The only way these days is to misuse DNS. But even that works less and less reliable.