Recently, Brian Krebs posted a story about the information shown on airline boarding passes. It’s interesting to see exactly how much secret/secure information is printed on a disposable piece of paperwork; much of it is secured only by format; barcodes are difficult for a person to read easily, so there’s no concern with it just being looked at. But there’s a trend for bragging about travel by posting photos of the boarding pass, and that’s where things get interesting.

Once there’s a picture taken, it’s possible to set a machine to read the barcode, and all that secret information is back out in the open, ready to be used and abused.

And this is hardly the only arena where this applies; the practice is known as “Security by Obscurity” and in a non-digital world it works fairly well. But we’re no longer in a time when, to search for a home ownership record, you have to spend thousands of man-hours in a county clerk’s file room, and with computers able to quickly and efficiently do all sorts of systematic work, it’s extremely difficult to keep things obscure.

So be careful with what information you make public, even in the most private spaces. It’s all too easy for it to seep back out.