Most networks today use a network based access control system to permit certain traffic and deny others. Since the inception of firewalls and web filters users (and malware) working behind them have strived to bypass the firewalls in order to do whatever it is they want to do.
Tunneling is a very common and effective way to bypass access control systems. Tunneling techniques can be used to bypass firewalls, Network Intrusion Prevention Systems, Web Security Gateways, and WiFi sign in pages.
more here............http://stephenperciballi.blogspot.com/2014/09/firewall-evasion-with-icmp-pingtunnel.html
Tunneling is a very common and effective way to bypass access control systems. Tunneling techniques can be used to bypass firewalls, Network Intrusion Prevention Systems, Web Security Gateways, and WiFi sign in pages.
more here............http://stephenperciballi.blogspot.com/2014/09/firewall-evasion-with-icmp-pingtunnel.html