It's increasingly easy to track individuals through various surprising means—including information found on printed documents. You must have printed a file for work from your home printer at some point. You took this printout to work and left it on your desk after using it. Someone with malicious intent can use this simple piece of paper against you.

It comes down to the Machine Identification Code. So how might your own printer be a threat to your security and privacy?

What Is a Machine Identification Code?

Xerox and Canon developed a technology called Machine Identification Code (MIC) in the 1980s. This added some dots that you wouldn't see at first glance to every sheet of paper that came out of the printer. The purpose of adding these was simply to identify the source of the printout. There's a clever and necessary reason for this: to tackle banknote counterfeiting.

Not many people noticed MIC for a consderable number of years. However, for the first time in 2004, ComputerWorld reported that the Dutch government used this technology to detect a group of counterfeiters printing fake money. Also in 2004, PC World magazine revealed that this system had existed for many years, in order to detect people who had been printing counterfeit money.

Diagrammatic representation of the MIC decoding process

In 2005, the Electronic Frontier Foundation (EEF) put together sample data it collected and figured out how the MIC works, meaning it became more widespread. Nonetheless, there's still not a lot of information about exactly how governments and companies use MIC technology. But some still claim that all the major color printer manufacturers have colluded with governments to ensure their printouts are traceable.

How Can Your Printer's MIC Threaten Your Privacy?

MIC technology places yellow dots on each printout in a specific pattern, depending on the model of the printer. It is very difficult to see these points with the naked eye under normal conditions, but it is possible to see them with very high-resolution scanners or under ultraviolet light.

Thanks to MIC technology, governments and all parties with access to the system can link up the printouts with which printers they came from. That essentially means you can be traced, or at least your home or work printer can be tracked; and then traced back to you.

From a forensic perspective, it's possible to use MIC technology to track down a criminal. If a note left at a crime scene is from a printer, it is possible to obtain information about the make and model of it using the MIC. And in doing so, the police can narrow down the search area.

That's a fair reason to use MIC, but imagine you're a journalist or activist: it's troubling for anyone who wants to be anonymous (or indeed pseudonymous).

How Can You Be Protected?

MIC yellow dots on a sample printout

To be protected from problems arising from MIC, you can check whether the printer you already have or plan to buy includes the relevant feature. The H-Node website is a directory of hardware working with free software; you can find information about whether each listed printer uses MIC.

Another method is to manipulate the MIC data. In 2018, a group of scientists at the Technical University of Dresden achieved just that. These scientists developed a tool called the deda, which makes it possible to anonymize the MIC data on anything coming out of your printer. That would mean you could take an effective step to ensuring your security and privacy.

Either way, you need to be aware that your printer contains lots of sensitive data about you; fortunately, you can do something about that.

Hardware Security and Privacy

Even a seemingly innocuous printer may be collecting information about you. This is not just for malicious purposes. The policies followed by states, large companies, and advertising agencies may require such data collection. Better to have a government record your information than be exploited by a hacker, right? Still, it could affect your anonymity, and what ultimately matters here is what you think about intrusions into your freedom.

You should make sure that you research the privacy policies of the printers and other hardware you use and the technologies behind them. Then ask yourself if you want to accept those terms or find an alternative.