Two men (22 and 28) are being detained in Tallaght Garda station on suspicion of defrauding ATM customers.
The scheme operates by inserting a plastic device in ATM machines that retains the card. The customer, who cannot retrieve the card, leaves to report the incident.
The alleged fraudsters, who watch the customer punching in the PIN number, then move in, remove the device and withdraw money from the account.
Gardai are retaining a number of devices found on the men for further investigation.