Wi-Fi can be used to track and monitor humans. Here’s how.
In the movie The Dark Knight, Batman turns every cellphone in Gotham City into a “high frequency generator” which emits electromagnetic waves. By scanning the waves, Batman creates a three-dimensional image of any environment where there is a cellphone, “seeing” the people and objects in that environment.
Batman uses the technology to find the Joker and save the day. But at the end of the movie, the technology is destroyed so no one else can use it to spy on Gotham’s citizens again.
The scenario may not seem as fantastical today as it did when the movie was released in 2008. Now, human rights organizations and privacy advocates have brought more attention to issues of mass surveillance and privacy. Figures like Edward Snowden and Mark Zuckerberg have put the spotlight on privacy (whether intentionally or not.)
Now we are learning that we are constantly surrounded by a device that can act very similarly to Batman’s improvised technology. It can “see” keystrokes on a computer, identify people by the way they walk, and more. No, it’s not a cellphone. It’s a Wi-Fi router.
It’s true. Wi-Fi can be used to track and monitor humans. Here’s how.
How Your Wi-Fi Router Can Track Your Movements
Most of us understand some Wi-Fi vulnerabilities. We know unsecured Wi-Fi networks make it easy for hackers to access the information on our computers or distribute malware.
These concerns are about cybersecurity and who is able to access our information. Not as many of us realize Wi-Fi can also reveal things about our physical selves—what we’re typing, how we walk, even what we’re saying.
When we move through a space with a Wi-Fi signal (which is almost every space, these days), our bodies absorb some of the Wi-Fi waves and reflect others in different directions. Researchers can analyze the ways a Wi-Fi signal is changed when a person moves through it, and from this information they can track what the person was doing as they moved through the signal.
This sounds like something straight out of a sci-fi movie, but it’s really happening. Researchers at Northwestern Polytechnical University in China conducted experiments that found a Wi-Fi router system they developed, called FreeSense, could learn to accurately identify people as they walked into a room. In 2013, researchers at MIT found they could use a router to detect the number of people in a room and identify their arm gestures, even through a wall.
Other researchers have developed WiKey, which uses Wi-Fi signals to identify keystrokes as they type. There are still limitations to this technology—it can’t pick up on keystrokes if there is any interference in the room, for example—but WiKey can recognize a sentence as it is typed with 93.5 percent accuracy.
Another system uses the distortions in Wi-Fi signals caused by moving mouths to lip-read. Wi-Fi can’t only “see” people’s movement and locations, it can “hear” them, too. When one person was speaking, the system could identify their words with 91 percent accuracy.
All it takes is some custom code to turn a router into a monitor. Given the ubiquity of routers and Wi-Fi, the potential scale of this is staggering. The Dark Knight no longer seems at all farfetched.
To be fair, these systems are experimental and currently work only in very controlled environments. But like all technologies, they will evolve and become better than they are now.
The Practical Applications of This Technology
Like all technologies, this ability to monitor people via Wi-Fi signals can be used for good or for not-so-good.
Many researchers exploring Wi-Fi sensing technology view it as a way to protect privacy while still capturing important information. After all, it’s less intrusive than a camera set to record everything that happens in a room. The FreeSense researchers believe their system could eventually become accurate enough to sound an alarm if an unrecognized intruder entered a room.
They also believe FreeSense could be connected to other smart devices in the home to optimize the home environment for specific individuals. If the router sensed a certain person had entered a room, it could tell the lights, appliances, and other connected devices, to customize the room to their preferences.
Emerald is a product that uses this technology to monitor physical activity in a home and send alerts if someone has fallen. Emerald even tries to predict falls before they happen. While this technology is geared towards elderly people, it’s easy to see that it could help people of any age who have mobility issues, or those who suffer from seizures. New parents may also find uses for the technology with their young children.
It’s also possible this sensing technology could be integrated into virtual reality technologies for tracking people’s movements. There are many potential applications of the technology, including many applications we probably haven’t yet considered.
But there’s another side to how this technology could be used. As Kaveh Waddell at the Atlantic put it:
“Routers could soon keep kids and older adults safe, log daily activities, or make a smart home run more smoothly—but, if invaded by a malicious hacker, they could also be turned into incredibly sophisticated hubs for monitoring and surveillance.”
In The Dark Knight, a similar technology was destroyed because it was considered too dangerous for it to fall into the wrong hands. In our world, this could become another technology to make us more vulnerable to hackers and cybercriminals (or even our own governments). You may want to know if your elderly mother has fallen in her home and has asked for help, but do you want anyone else to know it too?
It remains to be seen when this technology will be commonplace in homes and business, and how computer scientists will make it secure to minimize the threat of security and privacy breaches.
