Burglars are using coded chalk symbols to let other criminals know whether a property is worth targeting. The marks, dubbed the Da Pinci Code, are made by would-be thieves to indicate if the house is vulnerable, revealing who is living in the house and whether there is anything worth stealing.  IF YOU NOTICE THESE MARKINGS AT YOUR PROPERTY REMOVE IMMEDIATELY   Code: Would-be criminals scrawl the markings on properties to indicate whether the house is worth targeting