South Africa can be a dangerous place; in the past you could be attacked by roving bands of lions (which could still happen today, but unlikely in an urban setting), and today you could be attacked by a band of thugs.
Every mall and shop that I have seen has a sign similar to the in the picture. The houses all have high walls and fences topped with 10,000 DC volts of electricity, and some add razor wire as well.
Car doors auto lock, and there is an indicator light near the rear view mirror alerting you that the doors are locked.
People here seem to be very alert to their surroundings, but not in a hyper-paranoid way. Keep you possessions out of sight in the car, keep you pockets buttoned, don’t walk alone, close the gate, keep the doors locked, windows up. …
Just to keep things interesting last night at about 2:30am the alarm for the house went off – nothing like the sound of the siren to get your blood going. Turned out to be nothing, likely a spider walked across one of the sensors.
I got back to sleep after about ½ hour.