What type of firewall bypassing technique was used by the attacker?

The Rhythm Networks Pvt Ltd firm is a group of ethical hackers. Rhythm Networks was asked by their client Zombie to identify how the attacker penetrated their firewall. Rhythm discovered the attacker modified the addressing information of the IP packet header and the source address bits field to bypass the firewall.

What type of firewall bypassing technique was used by the attacker?
A . Source routing
B . Proxy Server
C . HTTP Tunneling
D . Anonymous Website Surfing Sites

Answer: C