Latest figures released by garda analysts reveal around four burglaries every week now involve the use of adapted fishing rods or long bamboo canes to snag keys left on hallway tables.
Hooks or powerful magnets are attached to the end of the rods to catch the unsecured keys, often left within a few feet of the front door.
Gangs are then able to steal cars without triggering alarms or break into homes without smashing windows or doors.
Last year, a teenager was jailed for two years for stealing a garda patrol car after taking keys from a garda’s house in a “fishing” style burglary.
In its latest internal study on burglaries in Ireland, the garda found more than 100 cases involving car keys being “fished” through letterboxes between July and December last year.
Around a fifth of all cars stolen are by criminals using the same tactics.
Despite an overall drop by nearly 9% in burglaries last year, Sergeant Kelvin Courtney, of the National Crime Prevention Unit, warned householders to remain vigilant.
“Burglars will tend to go for what they view as easy targets – houses with no lights on, no alarm, or unsecured doors and windows,” he said.
“So it is critical for householders to secure all doors and windows, light up their homes even when out, and have an alarm and turn it on even when at home.”
Around €10.7m worth of jewellery and cash, the most common items stolen, was taken during burglaries in the last six months of last year.
The latest analysis also revealed around a third of all burglaries happened between 5pm and 8pm. Just 15% happen overnight.
Jewellery and cash account for around three-quarters of ill-gotten gains.
And coming into the spring, it was warned that three in 10 house burglaries in warmer weather involve intruders coming through unsecured doors or windows.
Burglars are most likely to break into a house through a rear window (28% of cases), followed by a front door (27%) and rear door (25%).