[Peter_]

Once again it is not possible for him to use your connection as you have a cable coming into your property that then goes into your modem.

That modem is provisioned on your account and no one elses account.

So you state that you have no router and that you connect via ethernet directly to your computer.

If the above is correct then it is physically impossible that he is using your connection.

He has probably bought an illegal modem from Ebay and is obtaining broadband illegally but not your broadband.

As I said above if he had managed to clone your MAC address then he would be on the internet and you would not be until he switched the modem off.

To get broadband from your connection he would need to have an ethernet cable in your modem.