Burglars are apparently using secret symbols and codes to signal a house is ripe for robbery.
An increasing array of codes and marks are being left on buildings to show your home could be a target for burglars.
The Mirror previously revealed residents were left terrified their homes would become next after chalk marks were put on their walls.
But a variety of different, sometimes innocent-looking signals could point to houses being 'marked' because their owners have expensive or designer dogs which police say can be hugely lucrative for criminals.
In April, The Mirror told how homeowners were "petrified" because the method is often associated with burglaries and has also been linked to dog thefts in the past six months.
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Several homes in Desborough, Northants, had chalk marks lefts on walls, families people into a panic.
Reports of a fake salesman were confirmed by a company who the 'salesman' claimed to have represented.
Gemma Smallbones discovered the marking after answering the door to a man who claimed to be from supplier Utilita.
She said: "He was acting strangely, stood really close to the pane of glass in my front door like he was looking through it, he didn't step back when I opened the door.
"He made me feel uncomfortable so I just wanted to get rid of him.
"When he had gone I checked outside and found the chalk marking and this made me feel petrified for my family and my dogs. Obviously we had been targeted for something but we don't know what."
Officers in West Yorkshire previously published a list of the symbols, which were branded the 'Da Pinci Code ' after chalk marks began appearing on walls there.
But other signs and signals could be left by a criminal element planning on targeting.
They include signs for "nothing worth stealing", "wealthy" and @good target".
The Mirror Online contacted the National Police Chiefs' Council for comment.
