Police seized an ATM card skimming device in Sydney's inner west yesterday following a tip-off from a security guard.
The guard contacted police after he "observed an irregularity" with the machine on the ground level of a shopping centre in Drummoyne.
"Initial investigations suggest the device had been in place for no longer than five hours," NSW Police said.
They advised anyone who might have used the terminal between 9.30am and 2.30pm yesterday to contact their financial institution.
The discovery came on the back of a number of recent skimming cases.
Last March, thieves used ATM skimming devices to steal as much as $500,000 from a single terminal in the Melbourne CBD.
Compromised EFTPOS devices in Perth last October reportedly netted criminals $150,000.
NSW Police charged six people in January over a major eftpos terminal skimming scam in Sydney.
Fake cards that used PIN details skimmed in NSW were then believed to have been used in a spree in Melbourne this month.
A Malaysian man believed to be linked to the syndicate has been extradited from Brisbane to face charges.