For the first time in Australia, highly sophisticated card skimming devices have been found connected to ATMs in Brisbane.
The technology was installed over the top of ATM card slots across Queen Street Mall, which police say have put thousands of people's accounts at risk.
"It's a perfect time to strike because of the high volume of turnover in the ATMs," Detective Superintendent Brian Hay of the fraud squad told News Limited.
"We know cards have been compromised over the days prior to the discovery and we know money has been withdrawn from accounts.
"We also know the fraudsters have had possession of these devices, we suspect, for the last five months.
"We've heard of them in Europe but it's the first time we've seen them in Australia."
One device was found when a customer noticed it connected to one of the big four banks' ATMs, which was reported to the fraud squad.
Tiny cameras are attached to the top of the device, which police say would not have taken the fraudsters long to have placed on the ATMs.
"Once upon a time it would have taken them longer because they had to fit a camera up the top. This is all in one. That would take them five seconds to fit," Supt Hay said.
"When they go back to retrieve it they pull it off, plug it into their laptop then and there and it downloads all the data for them. They recharge, reset, clear the memory and go again,"
Supt Hay also said, despite the intricacies and sophistication of the device, they are not overly sturdy and can come loose.
"Beware of anyone acting suspiciously around ATMS and report it. Always give the card entry point a bit of a wiggle to make sure it's firmly and completely attached," Supt Hay said. "It's going to look flush but you've got a seam line on the outside which is not normally there," he said.