SPECIALIST Romanian gangs who travel the world targeting consumers with sophisticated card skimming technology are back in NSW.

Police have warned consumers to be vigilant with credit and bank cards after an increase in skimming offences with at least 15 ATMs hit so far and about $100,000 stolen.

"These devices are very sophisticated when compared with those from the past ... It's virtually undetectable," Fraud and Cybercrime Squad commander Detective Superintendent Col Dyson said.

media_camera Cheap and easily disguised the devices are expendable but can provide the gangs with a massive windfall.

"Every time these groups come through, the devices get more sophisticated.

"The latest lot are manufactured with 3D printers for specific ATMs."

Det Supt Dyson said the small devices could be installed on units in a "matter of seconds" and allowed criminals to record the card's data while a camera videoed pinnumbers.

The data was then broadcast to a member of the gang waiting in the area.

"They'll be in the vicinity because the technology they use broadcasts the data," he said. "They don't even necessarily need to retrieve the devices anymore."

While he would not confirm the gang were Roma gypsies he said most of the stolen cash had been sent to Romania - where the crime gang is believed to have originated.

"It's every two or three years they come in," he said. ''We arrest and charge them and they go away and leave us alone for a while."

media_camera The devices can be installed in seconds and provide the gangs with all the information they need.

Det Supt Dyson said the gang behaved "like tourists" moving around the country and would stay in areas where they commit their crimes.

A Romanian national has been charged with fraud and remains in custody to reappear at Central Local Court on September 10. Police urged bank customers to cover the keypad when entering pin numbers.

media_camera The devices that the gangs use are very small and difficult to detect.

media_camera Police are warning consumers to be vigilant with their credit and bank cards with a card skimming gang targeting automatic teller machines (ATMs) in NSW.

'The gangs may still gain the data but that is virtually useless to them without the pin," Det Supt Dyson said.

Most of the targeted ATMs were in the southern suburbs and northern beaches, with units in the city's west and CBD also impacted.