You can't detect (or, at least, it's exponentially harder to detect) someone simply listening. If they're broadcasting, then there's a source that you could lo

You can't detect (or, at least, it's exponentially harder to detect) someone simply listening. If they're broadcasting, then there's a source that you could look for and triangulate. On the flip side, however, it's nary impossible to search for someone listening in, as there's no 'signature' other than a big goofy looking antenna. ProxyHam is actively re-broadcasting a signal, so there's a source and a direction vector that anyone could see.