Motorists parked at the Manchester Fort Shopping Park were able to lock their cars doors on Sunday evening as a result of the attack by persons as-yet unknown.
Drivers would manually lock their vehicles but car boots were still left unlocked in some cases, leaving some with no option but to wait with their cars,
In addition to leaving cars open, the bungling thieves set off multiple alarms.
The attack was probably carried out using a £30 jamming device bought over the internet. Such devices have been the subject of recent police warnings via local paper, the Manchester Evening News.
Thieves jam radio frequency signals using the device so that when a mark attempts to lock their car with a remote fob, the signal is lost and the car can not be locked.
The same devices allow crooks to bypass car coding and re-program vehicles before driving the vehicle away.
Eye-witness Autumn DePoe-Hughes, who uploaded a video to Facebook, said:
"It was very eerie and there were so many confused people trying to lock their doors to no avail. Someone else had complete control over all of our cars for well over half an hour."
She said as far as she knew nothing was taken and the incident was not reported to the police.
"We were there for at least a half an hour and, according to people around us, it had been going on before we got there. It was continuing as we left, so I don’t know how long it continued on.
"The mall was closing up for the day and we had no way to secure the boot of our car, so we left. We were unable to lock the car with the fobs throughout our time there and the same happened to those around us, including one very confused mother.
"I went around speaking to people and they all confirmed that they could not lock their cars and couldn’t figure out what was going on. They all thought their cars needed to be repaired.
"The incident has all sorts of implications. If thieves steal something from a car using the tactic then they won't have to go old school and force open locks. That means that victims will be left with a harder job to claim for their losses against car insurance because it will be difficult to prove they locked their car prior to the theft, leaving insurance firms free to deny liability."
Ken Munro, a director at security consultancy Pen Test Partners, a security researcher who has investigated aspects of electronic car insecurity in the past, said electronic jamming devices were probably behind the incident.
"It’s basically the opposite of the amplification attack carried out against keyless entry cars.
"There have been a spate of thefts reported which appear to be linked to devices used to amplify the signal from your keys whilst in your house. The car unlocks outside on your drive, as it thinks the key is now within range, the thief gets in and drives off.
"This attack is more about jamming the radio signal from the keyfob to the car
"Jammers are readily & cheaply available online from overseas sources, though even possession may be illegal, depending on the country you’re in. It’s also fairly easy to make a jammer from components available at electronics shops.
"If one can jam the signal, the user can’t lock the car, so the thief may be able to jump in and steal it. Some vehicles allow keys to be programmed from the on-board diagnostics (OBD) port, which the thief has access to once inside the car, though this varies."