Ok...so you're afraid your system is going to get hacked through the port this game uses....

If you answer yes to the following questions:
Do you have any type of file sharing enabled on your computer, especially with P2P file sharing programs?
Are you using AIM, IRC, MSN Messenger, Yahoo Messenger?
Is the "guest" account still enabled on your computer?
Is the "help assistant" account still enabled on your computer?
Is the default "administrator" account not password protected with a minimum 16 character alpha numeric password?
Are there any user accounts that you created on your system that are not password protected?
Are you using the default "administrator" account as your own?
Do you connect your computer directly to the modem instead of using a router?
Have you been on any websites that installed some sort of malware on your computer?
Do you frequently find trojan files on your system when doing spyware/virus scans?
Do you have remote desktop enabled?
The possibility of someone accessing your system through the port a game uses for connectivity is slim but if the answer is yes to any of those questions then the possibility of your someone accessing your system is higher than average.
I would tell you to just cut the cable that connects your computer to your internet connection but I'm sure you get the idea of what not to do and what you can do to close most of the doors for accessing your computer remotely.