How Bluetooth Surveillance Works

By: John Fuller  | 

Person with Bluetooth earpiece in ear
If you own a Bluetooth device, can someone trace your activity?
Siri Stafford/Getty Images

­If you were to randomly pick up a piece of electronics equipment in your house, there's a reasonable chance that it has Bluetooth capabilities, especially if the gadget in question is fairly new. Whether it's a cell phone, smartphone, laptop, printer or keyboard, Bluetooth wireless technology has made life easier for those of us with too many electronics on our hands. Bluetooth devices get rid of frustrating wires and expensive adapters by using short-range radio signals to connect devices to each other and send information back and forth.

Bluetooth is especially common in mobile phones, which make up more than 60 percent of the Bluetooth market [source: Bialoglowy]. Bluetooth headsets, for example, transmit calls from your phone to the headset in your ear -- this allows you to keep your phone in your pocket, backpack or handbag while walking around. It's also helpful to drivers wanting to cruise around hands-free [source: Bajarin].

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Imagine, though, talking a walk through a crowded area -- perhaps the shopping district of a big city. Maybe you're just doing some casual window shopping, and you've kept your phone with you and left Bluetooth on "discoverable" mode. This allows other Bluetooth phones to locate you. As you linger in front of a shoe store and consider a new pair, your phone beeps: Someone's sent you a text message. It reads: "We know where you are. Having fun shopping?" Sounds like something out of a movie, right?

Such a thing is possible, and it's happened before. In fact, it's the very nature of Bluetooth -- a technology that can search for and locate other devices that also have Bluetooth -- which has some people concerned. Security has long been an issue with this technology -- bluejacking, for instance, although simply a harmless prank, allows Bluetooth users to send out unsolicited messages to nearby devices. Because Bluetooth devices are to some degree traceable, the concept of Bluetooth surveillance has been introduced into the tech world.

The phrase Bluetooth surveillance might conjure up images of Big Brother in George Orwell's dystopian novel of the future, "1984," but is that really the idea? How does Bluetooth surveillance work, and who would use it? Can it be used for good or for evil? To learn about Bluetooth surveillance and whether or not you should remain discoverable, read on.

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Bluetooth Discoverability

Person with earpiece
Keeping a Bluetooth device in "discoverable" mode allows other gadgets with Bluetooth to locate it within a certain range.
Elizabeth Young/Getty Images

Before we dive into Bluetooth surveillance, we'll want to take a look at how Bluetooth itself works and understand what makes the technology traceable. Bluetooth devices use the free, 2.4-gigahertz radio band known as ISM, which stands for industrial, scientific and medical devices. The band is unlicensed for low-power use, so headsets and other Bluetooth accessories use very little in the way of batteries. While any two Bluetooth devices can share ­data at a range between 10 and 100 meters (33 and 328 feet), phones usually operate at the former, laptops at the latter. Any Bluetooth device can communicate with up to seven other devices at a time.

After you turn any Bluetooth-capable device on, the most basic security feature on it is the ability to go into one of two modes: "discoverable" or "non-discoverable." This information is typically found in the "settings" option of a device's control panel, where you can select whether or not your phone or laptop is visible to others within the area.

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If several Bluetooth devices are set on discoverable mode, they all have the ability to search for and locate each other, so long as they remain within range. Every device has its own address, a unique 48-bit identifier with six bytes of information that might look like this: 01:23:45:67:89.10. The first three bytes (01:23:45) are assigned to the specific manufacturer of the device, while the last three bytes (67:89:10) are assigned by the manufacturer. These make each device entirely unique.

So how could someone track your movement if you left your phone on discoverable? Would they have to follow you around all day long, or is there a simpler way? To learn how a Bluetooth surveillance network is set up, keep reading.

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Bluetooth Positioning and Tracking

Setting up a network of Bluetooth receivers that record the locations of specific makes the method of Bluetooth surveillance possible. Could shopping mall stores do this to track customers' movements?
Setting up a network of Bluetooth receivers that record the locations of specific makes the method of Bluetooth surveillance possible. Could shopping mall stores do this to track customers' movements?
Michael McQueen/Getty Images

Locating several Bluetooth users with a typical mobile phone is relatively simple: You just turn on your phone and search for every discoverable device. But you could only monitor the people moving in and out of your Bluetooth's range, which is most likely a 10-meter (33-foot) circle around you. If you wanted to track a specific address, you'd have to visually locate that person's physical device and follow it around all day, which would easily blow your cover.

Creating a Bluetooth surveillance network solves this problem. If several Bluetooth-enabled receivers are strategically placed to cover a large area, they can track the positions of any discoverable device, recording and sending any data back to a single address. Each Bluetooth receiver acts like any regular Bluetooth device: It searches for every device within range. If a person walked down a 100-meter-long (328-foot-long) street and each Bluetooth receiver had a range of 10 meters, five receivers with a radius of 20 meters (66 feet) would be needed to track that person's movement. As he walked toward the street, the first receiver would track him for the length of the first 20 meters, the second for the next 20 meters, and so on for the length of the street.

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So how have people used this system to track people? One of the earliest uses of Bluetooth positioning and tracking technology is the Aalborg Zoo, the largest zoological garden in Denmark. The point of installing the system was not to put the zoo's patrons under surveillance or to see which exhibitions people went to more often. Instead, special "Bluetags" were made available to prevent parents from losing valuable belongings that tend to wander off -- their children. A parent could attach a "Bluetag" onto a child, and Bluetooth receivers around the zoo would track the child's movement.

Some people worry about others using this sort of technology illegally and maliciously. A shopping mall, for example, could install a Bluetooth surveillance system throughout its entire area to monitor the movements of Bluetooth owners. Although it wouldn't present a perfectly accurate description of a person's movement, the system could create a general map of his path and even compare how long someone stays in a certain area. With this knowledge, store owners could analyze shopper's behavior and change advertisement positions accordingly without anyone ever knowing.

It's difficult for someone to use Bluetooth to identify you in particular, unless you've chosen to include your name or some other personally identifiable information in the name of your phone, smart phone or PDA. Still, if you're concerned that someone might be able to track you down via Bluetooth, the best defense is to make your device non-discoverable to others when not using it.

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Originally Published: Jul 28, 2008

Bluetooth Surveillance FAQ

Can you track someone through Bluetooth?
Tracking Bluetooth users with discoverable devices is possible, but tracking someone specifically generally isn’t unless you physically follow them, which isn't practical.
Can Bluetooth be used for spying?
A Bluetooth recorder can be used for spying, but doing so requires a hacker to have direct access to the mobile device of the person they’re trying to spy on.
Can someone connect to my Bluetooth without me knowing?
Theoretically, anyone can connect to your Bluetooth and gain unauthorized access to your device if the visibility of your Bluetooth device is on. However, this is an unlikely scenario as modern Bluetooth devices require some kind of pairing sequence before successful connection. This makes it difficult for someone to connect to your Bluetooth without you knowing.
What is Bluetooth surveillance?
Bluetooth surveillance is strategically placing multiple Bluetooth-enabled receivers to cover a large area. These receivers can track the positions of any discoverable device in their proximity by recording and sending any data back to a single address. In this network, each Bluetooth receiver acts like a regular Bluetooth device, so if someone has walked down a 100-meter-long path and each Bluetooth receiver has a range of 10 meters, you only need five receivers with a radius of 20 meters to track their movement.
Can Bluetooth detect proximity?
No, Bluetooth can only detect if the beacon and receiver device are in proximity of each other, which is generally no more than 10 meters.

Lots More Information

Related HowStuffWorks Articles

More Great Links

  • Bialoglowy, Marek. "Bluetooth security review." Security Focus. April 25, 2005. (July 14, 2008). http://www.securityfocus.com/infocus/1830
  • Hallberg, Josef, Marcus Nilsson and Kåre Synnes. "Bluetooth positioning." Luleå University of Technology: Centre for Distance-spanning Technology, Department of Computer Science and Electrical Engineering. (July 21, 2008). http://media.csee.ltu.se/publications/2002/hallberg02bluetooth.pdf
  • Kostakos, Vassilis and Panos Kostakos. "Intelligence gathering by capturing the social processes within prisons." University of Bath: Department of Computer Science, Department of European Studies and Modern Languages. (July 14, 2008). http://arxiv.org/ftp/arxiv/papers/0804/0804.3064.pdf
  • Pogue, David. "Bluetooth and the end of audio wiring." New York Times. Aug. 16, 2007. (July 14, 2008). http://www.nytimes.com/2007/08/16/technology/circuits/16pogue.html?scp=1&sq=bluetooth&st=cse

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