The Secret Service is investigating a string of ATMs in Las Vegas which are debiting accounts without dispensing cash. But a similar scam in the city failed after picking the worst possible audience to attempt to defraud.

The IDG news service reports that several customers reported problems with ATMs in the Rio casino. Among them was Chris Paget whose account was debited $200 when attempted to withdraw that amount, but he received no cash. Paget says at least half a dozen other people experienced similar problems on machines at the venue, but staff refused to take action. Ironically Paget is a hardware security consultant whose work has covered credit card fraud.

While it’s possible scammers were hitting a jackpot at the Rio, they quickly busted in what was certainly an attempted heist at the Riviera casino. A man named Brian Markus noticed that the glass in front of an ATM’s built-in security camera was suspiciously smoky. When he shone a torch onto the glass there was no camera to be seen – but there was a computer which had been set up to capture data from cards.

To give them some credit, the scammers had skillfully picked a location for their fake ATM: in putting it near a security office they used one of the few spots not covered by the hotel’s security footage.

Unfortunately their timing wasn’t so great. Both Paget and Markus were in town for a conference held at the Riviera.

Specifically, the DefCon security conference, the world’s largest annual gathering of security experts and hackers.

(Pictures, courtesy of Flickr user bowbrick, show an unauthorized device fitted to the front of a grocery store ATM to read and copy card data.)