It’s one of the most hostile hacker environments in the country –- the DefCon hacker conference held every summer in Las Vegas.

But despite the fact that attendees know they should take precautions to protect their data, federal agents at the conference got a scare on Friday when they were told they might have been caught in the sights of an RFID reader.

The reader, connected to a web camera, sniffed data from RFID-enabled ID cards and other documents carried by attendees in pockets and backpacks as they passed a table where the equipment was stationed in full view.