How thieves/robbers mark your houses

I got this email from a friend today. Not sure if this is a hoax or just to scare people. Maybe our readers here can enlighten us how real is this threat:

Subject: Fw: Caution! How thieves/robbers mark your houses

This is taken from a newspaper article in local Chinese papers recently.
 

Take note of any unusual markings in front of your house.
 

It could be a code for these unsavory people.

Translation:
[ + ] or [ - ] means Owner not in house during day/night
[ Θ ] means Staying alone or Renting
[...] means 3 family members staying
[√ ] means House has been broken in before
[ *  ] means Target
[ X ]  means Not Target, Not Safe 

I guess this is what happens when even thieves and robbers get smarter after watching P. Ramlee's Ali Baba Bujang Lapok

Watch
Ali Baba Bujang Lapok Part 3/13