I have noticed several of the homemade cams use bright chains for security, I did too until I looked at some of the thick cables with black plastic coverimng on them. They are about the same price as chain.
I still like chains. I can cut a cable with a piece of steel with a sharp edge and a hammer. I weld a ring in one end of a 6' piece of chain. If the chain is new and shiny I paint the chains with Rustoleum rusty metal primer which is dark brown. I run the chain around the tree and through the ring and to a lock on the camera. The two cameras I have now are in ammo boxes and have a 3" pipe sleeve around the lock so it is inaccessible with bolt cutters.
There is no such thing as theftproof. But I try to make getting my cameras more effort than the average thief is willing to expend.
I also put as note like this in the camera box. "If you stole this camera and did not see the other camera covering the same area, I have your picture and will prosecute. If you return the camer and it is essentially undamaged and do not trespass again, this incident will be overlooked."
I agree that no cam is theftproof, however I don't think the average guy in the woods carries something to cut the cable. If he really wants it he will be back whether it has a cable or chain to get it. I thought about screwing my cams directly into the tree from the inside of the padlocked box.