Imagine that you are spending another boring day at work.
Let 's play a little with that dude over there who believes He knows everything...
Did you know that windows disconnect from the network when another pc has the same ip?
Now you know it!
The question is, how can i give my computer the IP i want?
Very simple if you follow these steps:
1) You must know the IP of the "victim". How?
If you are in a lan you can find it with a single ping.
ping victim.local.net where parameter is the URL of the victim.
After you see in console the "victim" IP.
2) Now we use a powerful program called nmap.
You can find it at http://insecure.org/nmap (yes it works on windows too).
For Ubuntu Linux use sudo apt-get install nmap.
For Gentoo Linux use emerge nmap.
In simple words nmap scans ports of remote computers.
3)Now you know the other computer IP (x.x.x.x) and you have nmap installed.
By simply typing
nmap -e eth1 -P0 -sS -S x.x.x.x x.x.x.x
at the desktop of the "victim" a pretty tooltip message appear
( Windows - System Error) There is an IP address conflict with another system on the network
4) That's it. The other computer is disconnected from the LAN and the INTERNET.
Soon dude will realise he is out. Don't betray your self.
You can help him connect again and repeat the steps...
If computers on the network have static IP you already know it.
If computers get their IP from a DHCP server you know what to do to get the IP.
Have fun and don't be bad...