
We can change IP easly in tunisia xD

Now I know there are hiding services and other tricks real hackers can use, but even those are not a real safeguard.
First of all your IP is the connection your PC has to the server of your provider. Regardless if you change it, it is still connected to your provider, and your provider has the obligation to know which client is connected to which IP at any time, as well as save this data for a limited time.
The police only has to give an official order and the provider will tell exactly that you were connected to an IP at a certain time.
Professional hackers will use several services that hide their IP, one can use different methods. However while they are actively hacking, traffic has to run from their PC to the end point. It is possible to add an identifier packet to the traffic that confirms certain actions, and this will give the IP to the police.
Such things are not available for someone attacking a game server, but attacking a government site is a different thing....