How do i make sure nobody else is using my internet without my permission?

First, be sure you have set up wireless security on your network. By default, wireless security is turned off on most routers and your network is completely open. Then only people who know the network key you create will be able to connect.

If you're worried about people guessing your wireless network key, enable MAC address filtering in your router. The MAC address is a unique value assigned to a network interface, and MAC address filtering denies access to any computer not on a list you create.Then, even if someone knows your key, their computer will not be able to use your network.

To prevent anyone plugging in a network cable to one of the router's wired ports, you need to prevent physical access to it. This might mean locating it in a room or cabinet that can be locked. Between keeping cables away and restricting wireless access, nobody will be able to use your Internet unless you let them.

You need to set up a network password to keep others from piggy-backing onto your internet connection and to secure others from accessing your data. I can walk you through the process if you give me your router''s manufacturer and model.