I built two heavy brackets out 5/16 x 2"steel flatbar and weldedlogging chain to one side. The entire bracket bolts to a tree using 3/8 lag bolts and the chain wraps around the tree and locks to bracket and crossbar that secures the camara into the bracket.

Not saying that would stop a determined thief, but it will stop the "opportunistic" thief.

A pair of heavy bolt cutters and a large hammer or 9/16 socket driver, and you could walk away with my camera and bracket.

Hiding the camera a little better and using a 'no flash' system would be more secure but more expensive too.