Computer networks communicate through the exchange of network datapackets, each containing multiple headers used for routing and to ensuretransmission continuity. One such header is the "Source IP Address",which indicates the IP address of the packet's sender.
In IP spoofing, also known as IP address forgery, used to gain unauthorized access to machines, whereby an attackerillicitly impersonate another machine by manipulating IP packets.
The intruder sends messages to a computer with an IP address indicating that the message is coming from a trusted host. To engage in IP spoofing, a hacker must first use a variety of techniques to find an IP address of a trusted host and then modify the packet headers so that it appears that the packets are coming from that host.
Robert Morris first conceptualized IP spoofing when he uncovered what isknown as sequence prediction within TCP. Morris noted this to be a gapin IP security. Certain design problems in the TCP/IP suite has lentitself well to cracking IP security and thus enabling IP spoofing.