you have a moat!
The last physical barrier is a moat. Moats surround part or all of a facility and are excellent physical barriers because they have a low profile and are not as obtrusive as fencing. In this instance, the consideration would be the depth and width. As with all physical barriers, the moat must be well maintained.
No, I am not kidding. The book actually suggests that a moat is a physical defence. I can just see trying to sell this to my boss now.
“Uh, Joe? I feel our revised security plan really needs a moat.”
“Did you say ‘a moat’?”
“Yep, it’s right there in the Security+ cirriculum. A moat, Joe.”
“With alligators, if you think we can manage to get them through the budget.”
Oh, God help me. What am I doing in this business? If it weren’t so damn funny, it’d make me cry.