IP spoofing happens when an intruder attempts to disguise itself by pretending to have a source IP address of a trusted host in order to gain access to resources on a trusted network. Using an IP address of another known host or known network, the attcker attempts to send and receive traffic on the network. The attacker is then able to use network resource that are associated with that sepcific IP address. Once the attcker has got access with IP spoofing, he can use this access for many purposes.