Kiwi Barnaby Jack wowed an American crowd this week by making cash spew out of an ATM machine like magic.

But although he was in Las Vegas, Mr Jack is no magician - he's a super hacker.

The 32-year-old Aucklander, who has lived in the States for six years, was demonstrating how to hack into the computer system of an ATM to force it to give up its cash at the Black Hat tech security conference in Vegas on Wednesday night.

One method took Mr Jack a couple of seconds after he physically approached the ATM but for the other, Mr Jack hacked into the machine remotely from his laptop.

If it sounds like a criminal mastermind's dream, it is. But Mr Jack is using his knowledge for good, not evil

"The goal definitely isn't to give a cookbook recipe on how to break into ATMs," he told nzherald.co.nz from Las Vegas today.

"It's more to raise awareness of the weaknesses. If the ATM vendors are aware of the weaknesses, they can implement protection mechanisms."

He decided to investigate ATMs because "people see them as this inpenetrable device, and no one had really looked at the underlying software". So he did, and found flaws - big ones.

So Mr Jack spent a couple of years sitting in his apartment in San Jose, California, tinkering with ATM machines he bought online until he perfected his methods.

The New Zealander's impressive skillset is entirely self-taught.

"It seemed like it was an interesting thing to know so I bought a few books and read up on it," he says.

At the end of the nineties, still living in Auckland, Mr Jack released a software tool that got him noticed. That got him invited to a Las Vegas conference, and a subsequent article is what really made people in the industry get interested.

Within days of the article being published, offers of work flooded in from companies all over America, and he's been Stateside ever since.

Mr Jack is now head of research at cybersecurity firm IOActive.

Asked if it's a well-paying gig, he coyly admits the money's "not too shabby".

He was originally scheduled to speak at the Black Hat conference a year ago, but his talk was pulled over concerns that protection software for the ATMs wouldn't be ready in time.

This year, then, the Kiwi entrepreneur was the conference's most anticipated speaker and his presentation expected to have wide implications for the industry.

Through his company, he now wants to work with ATM manufacturers to make their products safer.

Asked what's next on the horizon, the hacking whiz says he would like to look into the security of medical devices.

"I'm interested in things that, when they're compromised, have direct and immediate consequences," he says. "Whether it be ATM machines, medical devices or the computer system in your car, society relies on these devices but they're often overlooked by security researchers. But they have serious flaws that need to be discovered."