The markings are used by burglars to communicate with each other and let each other know which properties are easiest to break in to, and which should be avoided.
The signs were highlighted by Lanarkshire Police Division in 2015.
Meanings include ‘alarmed house’, ‘previously burgled’, ‘good target’, and ‘vulnerable occupant’.
Others are ‘nothing worth stealing’, ‘too risky’, ‘wealthy’, and ‘occupants afraid’.
Officers in West Yorkshire had previously published a list showing almost identical signs and symbols – which was later branded the ‘Da Pinci List’.
Experts from Yale, the home security specialists, have spoken to Express.co.uk to advise homeowners what to look out for, and what to do if they are concerned.
Revealing where to look to see if the signs are on your home, Yale said: “These markings are usually found on the property itself, but have also been detected on pavements, curbs and roads close by.
“White stones and advertising stickers attached to bins with fake locksmith contact details have also been used as a way of marking vulnerable properties.”
The markings are an issue Yale have been aware of for years. They said: “Pre-burglar marking is an issue we have been aware of for a long time. It involves criminals marking homes that are vulnerable or empty as a sign to other criminals, as well as acting as a reminder about which properties they should target.
“The markings are thought to provide potential housebreakers details about the building, such as whether it is a good target or has an alarm, or whether it has been previously been targeted successfully.
“Marks can also be used to flag up homes which are empty during the day or unoccupied for long periods of time.”
Research from Churchill Home Insurance found people who have been burgled have a one in four chance of falling victim again in the same property.
With that in mind, what should homeowners do to protect themselves?
Yale advised: “There are plenty of tips homeowners can follow to help protect their homes from burglary.
“Even something as simple as being on good terms with your neighbours will help, as they can keep an eye on your property when you’re away and alert you of any suspicious activity.
“Updating your home security system is also vital in protecting your home from thieves as they work as both a great visual deterrent and in securing your property from potential attacks.
“Smart home alarms and CCTV systems are a must have, with statistics emphasising that homes with CCTV are 90 per cent less likely to get burgled.
“It’s also crucial not to forget the importance of utilising your traditional security measures, including cylinders and nightlatches. Making sure your lock is Kitemarked to a suitable standard protects your home against all known attack methods, shows opportunistic thieves that your security is of the highest quality, and is also an effective visual deterrent for burglars to move on elsewhere.”
Yale’s advice is backed up by the research carried out by Churchill Home Insurance, which found one in ten of those who had been burgled did not upgrade their existing security systems, making them more vulnerable to repeated attacks.
Dr Claire Nee, a psychologist at the University of Portsmouth who has worked extensively with convicted criminals, also agreed with Yale and Churchill.
She said: “While only a small proportion of burglars use these codes or work in ‘packs’ tipping each other off, householders should be vigilant and report anything to the police. Perhaps more importantly, homeowners should assess and address the natural vulnerabilities of their properties such as rear and side access and cues showing no-one’s home in order to reduce the chances of burglary.”