Two-dimensional barcodes and QR codes can hold a great deal of information, and the codes printed on airline boarding passes may allow someone to discover more about you, your future travel plans, and your frequent flyer account.

Earlier this year, I heard from a longtime KrebsOnSecurity reader named Cory who said he began to get curious about the data stored inside a boarding pass barcode after a friend put a picture of his boarding pass up on Facebook. Cory took a screen shot of the boarding pass, enlarged it, and quickly found a site online that could read the data.

"I found a website that could decode the data and instantly had lots of info about his trip," Cory said, showing this author step-by-step exactly how he was able to find this information. '

"Besides his name, frequent flyer number and other [personally identifiable information], I was able to get his record locator (a.k.a. "record key" for the Lufthansa flight he was taking that day," Cory said. "I then proceeded to Lufthansa's website and using his last name (which was encoded in the barcode) and the record locator was able to get access to his entire account. Not only could I see this one flight, but I could see ANY future flights that were booked to his frequent flyer number from the Star Alliance."