Check if someone or your neighbor is stealing your wi-fi

Eh? Two options: 1) you leave your wifi unsecured intentionally, and are hence willing to have bandwidth 'stolen' OR 2) you use WEP (I know, I know) etc or MAC address limiting to restrict access

Also, my modem's admin mode lists active connections, and can log activity.

So what was the point of this article again? Detection of use != prevention (as claimed by the writer)