Spoofing

[[SiN]]

I would say dont mess with it, its gaining unauthorized access to someones computer... which from what I know isnt something the law may like...

Quote:

IP SPOOFING

A technique used to gain unauthorized access to computers, whereby 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.
Newer routers and firewall arrangements can offer protection against IP spoofing.
http://www.webopedia.com/TERM/I/IP_spoofing.html

the definition should sound geeky enough to explain to yer friend.