Smartphone Signal Interception

Smartphone hijacking and theft of your personal information may not be exclusive to stalking, but they are ways a stalker can find you. As we discussed earlier, a stalker could use tracking software to target your smartphone and intercept personal calls and messages. But he or she could also stage a non-targeted attack on your smartphone using signal interception.

As described in How Smartphones Work, your smartphone has a combination of radios and signals it uses to communicate. For phone calls, text messaging and Internet browser, your smartphone uses one or more cell-phone network protocols like GPRS, EDGE and 3G. Depending on the smartphone, you might also have a short-range Bluetooth radio, a GPS receiver, and one or more radios for connecting to different WiFi networks. With all these signals moving through the air, it isn't surprising that stalkers often find ways to capture them and use them for cruel purposes.

Currently, Bluetooth is the easiest of these signals to intercept. Our article What is bluejacking? describes how someone can tap into your smartphone while its Bluetooth radio is on and discoverable. The bluejacker needs no more than his or her own Bluetooth device to do the trick. When the device finds your smartphone, the bluejacker connects and sends data that creates a new contact in your smartphone's address book. Though bluejacking itself is a harmless prank, it's also a warning that your smartphone could receive harmful, unwanted data if you leave your Bluetooth connect open. Your best defense is to restrict access to your Bluetooth radio: Don't enable it unless you need it, and control whether or not it's discoverable by unknown devices.

For the more dedicated and tech-savvy stalker, imitating a trusted connection point could be the weapon of choice against you and your smartphone. In the United States, cellular towers and frequencies are regulated by the Federal Communications Commission, and free wireless access points are available in more and more public spaces. However, a hacker subculture that predates mobile phones, known as phreakers, make a hobby out of building and using their own devices to imitate and manipulate such trusted connections.

While original phreakers adopted a set of rules that kept them out of trouble, today's phreakers are often out to do some damage. A mild-mannered phreaker who wants to stalk you can spoof a number, call your smartphone and taunt you after you pick up. More aggressive phreakers could steal your entire address book, upload malware or make long-distance calls from your smartphone.

Similar to bluejacking, your best defense against phreakers is to know your smartphone and limit your use of its radios and connections. If you don't recognize a number that's calling when you look at your caller ID, and you're not expecting a call, you could let the call go to voicemail instead of answering. If you're walking around busy public spaces and you're not using your phone's WiFi connection or GPS, turn off the WiFi radio and GPS features. Not only will radio limiting prevent unwanted connections, but it'll also keep your battery charged longer.

You can still enjoy your smartphone while avoiding stalkers and hackers. Just use these four tips as your defense: Know your smartphone, know its weaknesses, know how to keep it secure and keep your personal information personal. In the meantime, dial in to the next page for more great links about smartphone tracking and stalking.