In one case in which a team of burglars were caught on camera, a woman holding a baby is seen knocking on the front door. No one answers. Her partners then break into the home through the back.
In another case, two men were seen on camera kicking their way into a home. They then suddenly realize a camera just captured their crime. One of the men tried to knock it out, but it was too late.
"It's a pretty simple way to commit a burglary," said LAPD Commander Andy Smith.
The LAPD has arrested dozens of people suspected of committing so-called "knock knock" robberies in the San Fernando Valley and West Los Angeles. The thieves are in and out in seconds.
"They know that if a neighbor sees a bunch of people rushing in, they're going to call the police, which is exactly what we want people to do. However, they're in and out so quickly, by the time police get there, they've already left," said Smith.
Calvin LaPorte Anderson has installed cameras at dozens of homes just this year as more and more homeowners use surveillance to catch thieves and vandals. Forget the grainy pictures of the past. Today's high definition cameras clearly show faces.
And many of these cameras will send you live video of the break-ins -- as they are happening -- to your phone, tablet or computer.
One man, known only as Hasan, couldn't figure out why he wasn't receiving his mail. So he installed a $350 do-it-yourself camera under his roof, wired it to his computer and got the answer.
"I saw the young lady came into my driveway," he said.
While Hasan was at work, his camera detected motion and sent an alert to his smartphone. Someone just entered his property. He downloaded the video and saw the postman deliver a package to the front porch.
"This white car drives up and a young lady came out of the car and walked into my driveway," said Hasan.
The woman went directly to his front porch, took the package, took a quick detour to the mailbox, cleaned it out and jumped back in the car. Police now have that video, and so do the feds.
But a do-it-yourself surveillance system may not be for everyone. So what options are best for you?
There's a $150 "nanny cam" that sits on a shelf and transmits the picture wirelessly to your computer. There's also a $300 kit that comes with four cameras but requires running cable to a recorder. That takes a little more work. There's also a $249 wireless kit that comes with two cameras and a portable monitor, but you'll need a good Wi-Fi connection, and you need to be a little tech savvy.
Of course, any surveillance camera will help scare off intruders.
"When somebody sees a camera, they're more likely to turn around," said Anderson.