Those are made by CAMLOCKbox. http://store.camlockbox.com/camlockbox-heavy-duty-universal-swivel-bracket That page has a video that should give you a better idea how the mount works.
I've used a couple of them, with modifications because I was using the cams to detect thieves and other lowlifes. Because the cams were at around eye level, where someone could get their mitts on the security case and mount, I replaced the star knob with a tamper-resistant screw. It's a little harder to tighten after getting the cam aimed, but it discourages tomfoolery.
A year or two ago, I took down one of the two cams that I was using with the CLB mount. I think that one was hardly noticed because it was on a utility pole.
The one that's still up has drawn some trespassers' attention. Somebody tilted the cam slightly off its original point of aim once, but they couldn't do much more without resorting to serious tools. I have a Python cable lock fed through the swivel mount, through the camera case (and cam) and around a nearby cast-iron pipe, which makes it a little harder for someone to twist the case too far out of position. The cable lock is one more thing to fiddle with when I change the memory card, but it keeps the lowlifes from doing too much mischief.