The Register has a pretty interesting story on dot-matrix printers and data security. According to the article, researchers have been able to turn the screeches of printers into data. Boy, would it suck to find that, after ensuring that you’re using hard disk encryption and securing your communication channels, a decrepit printer is the cause of your data security woes!
Attack Only Works on English Text
But, I assume that’s because the researchers were conducting their studies in English (the researchers work at a German university). However, there is really no reason why one couldn’t take the same research and apply it to another language.
As far as I can tell, this is not a simple case where one particular screech is an “a”, another is a “b”, and so on. The article points out that specific sounds are linked to an “entry in a large list of English words.” Speech-recognition technology also figures as well.
The thankful thing about the technique–at least for the non-criminal minded–is that the sounds and the word list have to be calibrated, if you will, for each dot-matrix printer model. Furthermore, the researchers revealed that blocking the sound of a printer is an effective countermeasure.
Pretty Good Positive Rates
I would have dismissed the story as a fun-but-useless piece of research, but consider the success rates:
63% accuracy when the software analyzes it
70% accuracy when voice-recognition technology is used
95.5% accuracy when fine tuned (although, one wonders what “fine tuning” really consists of)
It was noted that the microphone picking up the screechy sounds must be about 2 cm (nearly an inch) away, and the further away the microphone, the less accurate the results.
Reason for Concern?
Maybe. In the US, about the only place that I remember seeing dot matrix printers is at banks. However, it turns out that 60% doctors and 30% of banks in Germany still use such machines. I imagine that the numbers could reflect the usage of dot-matrix printers across the world.
The idea is pretty far-fetched. Imagine the risks that a person would be taking to place a microphone and then retrieving the tape.
On the other hand, that didn’t stop people from installing cameras and card skimmers on ATM machines and gas stations. At one time, such actions were considered far-fetched, too.
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