ATM network Link is advising people to shield cash machine keypads when entering their PIN as a precaution against fraud.
The recommendation comes after the group obtained video footage showing how criminals target cash machines and steal customer information.
On machines that are targeted, the criminals fix a skimming device to the card entry slot to copy data from the card's magnetic strip. A tiny pinhole camera pointed at the keypad records PIN entered by the customer.
Link said the camera will be unable to capture this information if people took the simple step of shielding the PIN when typing.
The estimated loss from cash fraud was around £36.7 million in 2009. Although the figures are 51% lower from the peak of £74.6 million in 2004, banks are still urging their customers to be vigilant.
Edwin Schooling Latter, managing director of Link Scheme, said: "Incidences of cash machine crime may be few and far between but it is very difficult for a member of the public to tell if an ATM has been targeted or not.
"The best thing to do is always to be on the safe side and shield the keypad whenever you enter your Pin."