NEPEAN Regional Security chief, Gina Field, helped Penrith police catch a youth who had been harassing residents of a new housing estate.
Mrs Field said her company was contracted to look after security in the suburb.
"It started about four weeks ago," she said.
"This car came through the estate on Friday and Saturday nights, and the youth did burn-outs and threw eggs at houses and cars.
"Our own security car was hit by eggs, twice."
She contacted Penrith police and told them what she was doing.
"First, I observed what he was doing, recorded it, then reported that to the police," Mrs Field said.
"Next, I decided to do surveillance in an unmarked security car."
On the night of Saturday, August 11, she spotted the vehicle and contacted the police.
"I slowly followed the car, which went through Penrith," she said.
"I was able to contact the police, giving them updates.
"At one point he drove past Penrith police station, but the police stopped him and did a vehicle check at [the] High and Evan street intersection."
Police questioned the driver and arrested him at about 12.20am, August 12.
A spokesman for Penrith police said they were grateful for the help and that they would always follow-up any information given to them about illegal activities.
Mrs Field said it was a great example of a private security firm helping in law enforcement.