EggXpert

Well you can use someone else's network.

But think of things from this perspective: If you change your source IP, how will the server you are playing a game on know where to send all the game data packets to?

Example:

You are IP Address: is 192.168.1.16

You log on to Server @ 192.168.1.123

You run a "masking utility" that tells the server you are IP address 192.168.1.69

All of a sudden your game session freezes (and drops) because the server is sending all your positional and status data to 192.168.1.69... and you are still @ 192.168.1.16

You can "hide" your IP when browsing by using a proxy, but while there are http proxies all over I don't know of a single (efficient) "Game Proxy" server. It's theoretically possible, but you have to essentially MAKE one for every game you want to play, and run it at a remove site. It's not really feasible.

sjr:

Don't get banned in games and then you don't need to mask your ip for games.

haha :P  

Only technique that I know that will effectively mask you is a proxy server that either you own or by a company that you trust.

LOL @ sjr 

There are several companies with programs out for doing that, while you install there software, it will run through there "HUBS" to pass data back and forth, keeping you anonymous.

Pretty sure it works with games. 

But it would be cheeper just not to get kicked off.  

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Like GmsCool says, there are programs that is pretty much VPN. It sends all traffic to a proxy server |o.O|

I remembered there is a thread talking about how to do it in Tips&Tricks section; sorry, it's been a long time, i cannot find it for you ..