More than 200 cars were stolen last year by thieves using magnets or long hooks to 'fish' car keys through letterboxes.
More burglaries are carried out during the winter months and gardaí are asking people to be extra vigilant when it comes to home security.
Last year, burglars made off with more than €14m worth of jewellery and €8m in cash was stolen.
Sergeant Kelvin Courtney from the National Crime Prevention Unit said people should also protect themselves against the "fishing" craze.
"You want to make it as hard as possible for them to get through your letterbox," he said. "Maybe put a guard on it (and) have a postbox on the side of your door (rather than a letterbox)."
"We'd be asking people to store their keys (and) not traditionally throwing them on the hall table as soon as they come in the door."