A police force found more than 500 properties at risk of burglary during evening patrols.
Officers from Durham Police and Neighbourhood Watch volunteers targeted areas where there had been previous break-ins.
More than 3,000 houses in County Durham and Darlington were checked during the "dark nights" initiative.
Homes were found with garage doors wide open or left without lights and "clearly unoccupied", the force said.
Det Ch Insp Dave Ashton said: "We know that homes left in darkness are much more likely to be targeted by criminals."
The force is offering to supply homeowners with safety equipment such as lighting timers.