A security expert has identified flaws in the design of some automated teller machines that make them vulnerable to hackers, who could make the dispensers spit out their cash holdings.

Barnaby Jack, head of research at Seattle-based, security firm IOActive Labs, will demonstrate methods for “jackpotting” ATMs at the Black Hat security conference in Las Vegas that starts on July 28.“ATMs are not as secure as we would like them to be,” Jeff Moss, founder of the Black Hat conference and a member of President Barack Obama’s Homeland Security Advisory Council said. “(Jack) has a number of different attacks that make all the money come out.”

Jack declined to discuss his techniques before the conference. The world’s biggest ATM manufacturers include Diebold Inc. and NCR Corp. Officials with those companies could not be reached for comment.

Banks may cringe when he speaks, fearing would-be crooks will adopt his methods. But Moss said that going public will prompt ATM operators  to tighten security.

One potential route of attack is via communications ports sometimes accessible from outside an ATM, Moss said.

“You want everybody to know there are possible ways to jackpot these machines, so they will go and get their machines updated,” he said.

Joe Grand, a hardware security expert, said he was not surprised to learn of Jack’s research.

“People are starting to realize that hardware products do have security vulnerabilities. Parking meters, ATMs, everything that has electronics in it can be broken,” Grand said. “A lot of times a hardware product is just a computer in a different shell.”