Rural communities fear their properties are being marked with chalk to alert burglars of valuables inside.
One rural community has set up a 24-hour neighbourhood watch after a series of break-ins.
Locals in Clonaslee, Co Laois, believe farmers' homes in particular were being targeted, with stones and markings used to identify properties of note.
Local Joey Dempsey told the Irish Independent that houses in the area have seen "mysterious" markings outside before they were burgled.
"There was so much concern in the community that there is now a volunteer nightly patrol, seven nights a week," he said.
"Burglars are going one step further, creating stone mounds or markings with stones outside properties to be hit."
local farmer Joe Reilly said that farmers in the area were being robbed "left, right and centre".
"They were targeting farmers who were on their own and stealing their machinery. I believe the markings were used to later target houses."
Local businessman Paul Downey said that burglars had been seen on CCTV outside properties that had been hit.
"We saw two lads on CCTV going around the neighbourhood every night between 12am to 4am. I think it's legitimate that the houses were marked and then targeted."
Brendan Kelly set up the neighbourhood watch in the nearby town of Killoughy, Co Offaly, after a number of robberies.
"We set up the neighbourhood watch two years ago when we noticed a lot of break-ins in the area," he said.
"We have a team of about 42 people and every night somebody is on watch," he said. "It seems to be working because the burglaries have declined."
A Garda spokesperson urged the public to remain vigilant.
Earlier this week, locals in the Ballybrack and Shankill area, Co Dublin, became concerned after spotting distinct markings outside their homes.
One image of a chalk marking in the area shared by a local showed three Xs in a row, which according to a key suggests 'three good targets in a row'.
Local Fianna Fáil activist Vinny Durán-Kearns said similar markings had been used to target homes in the Dún Laoghaire-Rathdown area.
"Burglars have used similar markings to target houses in the area. We have a guide of what they might mean to keep locals updated," he said.