Network issues

Hi all,

I am not very pc savvy. However, I know that someone is hacking into my system. This computer was given to me and I think the person who gave it to me is hacking into it. How is this possible? How can I find out if this computer is linked to his home network, and how can I change my wireless password so that he can't hack through wireless???
Pls help.

Jay

You didn't supply much information..... If you have a router, go into the router setup menu and change the encryption for wireless to WPA2 and set in a strong password. You'll need to adjust your airport settings on your Mac Pro accordingly. Before going into the router menu, attach your machine to the router using an ethernet cable otherwise you may lose the connection entirely.

Regards.