I have been a big fan of paperless airline boarding passes almost since their introduction, and a recent post reminded me of yet another reason: they can become an easy way to compromise your identity. The reason is a combination of the low and high technology, all leveraging your smart phone’s camera.

The issue has to do with the way the airlines make it easy to use the printed bar code information to gain access to your flight details. Brian Krebs first wrote about this several years ago, and if you still use the printed boarding passes, the first thing you should know is that you shouldn’t post pictures of them on any of your social media outlets. Krebs found more than 90,000 such images exist when he did a quick search.

So here is what could happen. Criminals look for these photos, and could then use the QR code or the booking reference number to gain access to your flight details. Think about this for a moment. Let’s say you are on vacation, and you post your “here I am at the airport about to take off for a long trip on the other side of the planet” obligatory photo. Now someone comes along, and can change your return flight, or use this information to leverage more identity theft since the booking contains information such as your passport number and birthdate.

And of course, posting flight details is another way that criminals could decide to pay your unoccupied home a visit while you are away too.

Some folks purposely blur out the details about their name, but leave the barcode visible, such as this photo above, where we can find out her full name by scanning the barcode. Oops.

This method works for dumpster diving too. How many of us leave our used boarding papers on board the aircraft that we are leaving, thinking no use to me? I have done that several times. Again, someone could use that information to hijack my account. So avoid leaving your boarding pass in the trash at the airport or tucked into that seat-back pocket in front of you before deplaning. Instead, bring it home and shred it. And don’t take pictures of your boarding pass. Finally, be careful of spreading your “real” birthday around on social media. My “birthday” has been January 1 for several years: my real friends know when it actually is.

So go paperless when you can. And be careful what you post online.