Eavesdropping became popular as wireless networks became popular. After all, wired networks don't broadcast their data packets to the world and hope only the destination nodes are paying attention.
So just like you can't help but eavesdrop on a cell phone caller beside you at the movies, you can't always help being an eavesdropper in the world of wireless networking. But polite members of a technical society never consciously eavesdrop, and their proper response when an outside signal intrudes is to inform the network owner of the security leak.
You may never be able to stop wireless network signals from leaking out of your home or small office. People tend to put their desks around the walls and their computers on their desks. So if you have wireless connections that have a clear signal at the outside wall, the signal almost certainly goes through your walls and out into the world. Some companies are working on this, but the equipment has yet to be affordable for any but the largest companies. It will be interesting to see if the signal control tools do become inexpensive enough for home use.
Polite isn't the term for those who intentionally eavesdrop on networks. The correct term, in almost every case, is criminal. And with preparation, you can avoid being the victim of the eavesdropping criminal.
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