I was talking to a guy about villages in Africa. His unit would come into them and the story was always the same. For weeks or even months someone was murdering one or two of the males. Either attacking them physically when alone or sniping them from afar. Its called "dwindling" for lack of a better translation and it fits the crime sorta speak.
Two or three guys can "dwindle" a whole village down to women and children in a few weeks. Hit and run,... hit and run, rinse and repeat for weeks until the village had no one left to put up a resistance to the guys just walking up and taking what they want. They could also toss a ransom note into the village or whatever... pay up or lose more fathers....
You also got to remember evil isnt always in your face and obvious...it can also be concealed. The guy walking right up to the front door unarmed is just as much of a risk as the guy walking around at night with a gun. What you gonna do...murder every person who walks onto your land and asks for assistance?
Fence lines are only useful when there is a polite society and only keeps the honest person out. Do not waste too much effort on them. Repair and maintain what is needed, but don't go all out...people protect what is valuable... so a fence is also a clue to the bad guys.
Night vision is a MUST. Early warning is a must. Having a "first contact" policy in place that everyone knows is a must. Appear weak and vulnerable to test your guest. Their true nature will come out.
"Show No Mercy" to those who would offer you none.