They operate in the middle of the day, when many residents are at work and the delivery vans are making their rounds.
They tend to follow FedEx, UPS and U.S. mail workers down streets, on the lookout for packages they can nab. Some even dress in uniforms to avoid suspicion.
As Internet retailers make big gains against shopping malls this holiday season, "porch pirates" have been out in force stealing their piece of the pie.
Customers are increasingly using Amazon, EBay and other retailers to buy goods they previously purchased in stores — especially around Christmas, when UPS delivers more than 30 million packages per day in the week before the holiday.
The problem is that many of those package end up on unattended doorsteps, unlocked mailboxes and stoops. All this curbside commerce has created a new class of criminal dedicated to pilfering as many packages as possible.
Police say that in an era of heightened security at stores and shopping centers, porch pirating has become one of the easiest forms of petty theft.
Cracking down on the bandits has proved difficult. Some police departments have resorted to elaborate stings in which they leave package with GPS trackers inside in hopes of luring would-be thieves. Residents have installed high-tech camera systems that capture the crimes on tape, but the recordings have done little to prevent the thefts.
Police departments don't break out package thefts from overall crime numbers, but many officials say the problem is getting worse, especially around the holidays. One security services company estimated that 11 million people nationwide had a package stolen during the past year.
The bandits can look almost casual as they make their rounds.
A few weeks ago, a security camera captured a man wearing a yellow safety vest strolling up to a porch on Milan Avenue in South Pasadena. A huge box catches his eye. It contains an enormous trampoline destined for the family's Christmas tree.
The video shows him rolling the package down the brick steps. The box clangs as he struggles to get it into a car before driving away.
"It is the season for package thieves. It is a crime of the holiday season," South Pasadena police Det. Richard Lee said. "We get a lot of them caught on camera. But the setback of the houses means it's often hard to see the license plates of the getaway car."
Earlier that day, another man wearing a yellow safety vest struck nearby on Marguerita Avenue in Alhambra. He, too, was captured on home video.
Lee said the videos have helped with investigations — but usually only when the cameras are aimed properly. Recording the theft is one thing, but the main way police capture bad guys is by getting the license plate of the getaway car. So Lee urged residents to position their cameras so they have a good view of the street as well as the front porch.
Not surprisingly, an entire industry of home security has popped up to combat the front-porch thefts. Smart doorbells now send live video of visitors to your phone.
There are apps like Doorman that notify you when a package is delivered. A variety of front-porch lock boxes that bolt to the ground also are available. Amazon has even installed community lockers in some areas where customers can retrieve their goods.
"The reality is if you're a delivery driver, you will try to do the best you can to conceal a package, but you've got so many deliveries to make," Lee said.
While the thefts get more attention during the holiday, they are a year-round problem. And some police departments have gotten creative in combating the crimes.
On Dec. 4, a large package sat invitingly on the doorstep of a home on Lyndon Way in Arcadia. Police say Joseph Kamal, 40, and Cristhyn Amador, 21, walked up, grabbed the package and took off.
A short distance away, officers detained the pair. Inside the box was a GPS tracker, Arcadia police Sgt. Brett Bourgeous said.
"It notifies us the minute the package is lifted, and we can track it. It is very accurate," he said. "We have a team in place ready to swoop down on the suspects."
Investigators arrested Kamal and Amador on suspicion of grand theft and possession of a controlled substance. The sting was one of five the department has conducted this month. Bourgeous estimated they have led to 120 arrests in the last year.
The bait packages are deployed after investigators get reports of porch pirates working in a neighborhood.
"It is a crime of opportunity," he said. "These arrests mean our residents get the packages intended for them in the holiday season."
Other cities such as Redlands and Rancho Cordova conduct similar stings.
LAPD Capt. Paul Vernon said there are things that neighborhoods can do to reduce the risk of thefts, such as having packages delivered to an address where someone is regularly home during the day.
When detectives capture a theft suspect, they often find piles of pilfered packages inside their home.
That was the case with 32-year-old Elvis Babadjanian, police said. On Dec. 6, a witness saw him walk up to a house in Glendale and grab a package.
The witness jotted down the car's license plate, and Glendale detectives soon learned of another theft the day before in which the suspect had a similar description. A video shows a car passing the home before a man grabbed a parcel on the front porch, police say.
When investigators raided Babadjanian's Glendale home, they said they found piles of new merchandise and Amazon boxes. He was arrested.
Los Angeles police said a security video captured Tagui Abrayan, 41, darting from a white Mercedes and calmly grabbing a parcel off a Studio City front door last September. LAPD detectives said they found mail and packages in her home belonging to about 300 people across the San Fernando Valley, Malibu and the Westside, as well as a homemade mailbox key that could unlock apartment mailboxes.
LAPD Assistant Chief Michel Moore said some victims only tell their shipper about the missing packages and don't call police. Without such reports, he said, it's difficult to build any crime patterns.
But other homeowners are confronting the porch pirates. When an Alhambra resident pulled up into his driveway in May, he said he saw a woman calmly stealing his packages.
"You know I live here," he told the woman in a video that went viral. "If I were you, I'd put that down."
"Why?" she replied.
"Because those are my stuff," he said. "I live here."
"No, you don't. My mom lives here," she replied.
He started to call the police, and the woman dropped the packages and ran off. The video was replayed on local television. The woman, whom police identified as Rianna Medina, 20, eventually was arrested.
A family in Lodi had a different idea for deterring package thieves.
Amanda Torres and her fiancé were angry and frustrated after having Amazon packages stolen from their doorstep. So they decided to fight back by leaving decoy boxes for thieves, filled with dog feces.
Their security camera footage showed the same man who had stolen packages from their home in the past walking onto their porch and grabbing the boxes that had a stinky surprise inside.
Police are still looking for the thief, but Torres' scheme made national news.