One summer there was a team of daytime burglars operating in our little city. They would knock to see if anyone was home. If you answered they would apologize and ask directions to someplace and go away. If there was no answer, they would go to the back door and break in.
The police recommended knocking on the inside of the door and yelling “not interested, go away” or some such, just to let them know you were in there.
Then you can't plug them when they try to break in the back door. The trick is to wait until just after they have entered the premises, then they are fair game for doing society a favor.
That has always been the standard mode of operations for burglars in this area. Peak times for burglaries are Wednesday and Thursday afternoon when people are away from the house at work.
They go around knocking on doors and pretending to be "lost" if someone answers the door.
In an astonishing number of cases, the burglars simply walk through the unlocked front entrance if nobody is home.