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Seeing as mobile phones aren't sending signals when switched off, is it possible to track a mobile phone when it's switched off?

NSA growth fueled by need to target terrorists

By September 2004, a new NSA technique enabled the agency to find cellphones even when they were turned off. JSOC troops called this “The Find,” and it gave them thousands of new targets, including members of a burgeoning al-Qaeda-sponsored insurgency in Iraq, according to members of the unit.

At the same time, the NSA developed a new computer linkup called the Real Time Regional Gateway into which the military and intelligence officers could feed every bit of data or seized documents and get back a phone number or list of potential targets. It also allowed commanders to see, on a screen, every type of surveillance available in a given territory.

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    The question referred to explicitly talks about sending signals to track location. This is a duplicate.
    – DJClayworth
    Jul 23, 2013 at 3:25
  • Has the article you're linking to been edited? At least your quote is not contained in the article.
    – Tor-Einar Jarnbjo
    Jul 23, 2013 at 14:15
  • Claiming it can be done and providing a plausible mechanism are not the same. Unless someone can show how an external signal can be received by a phone turned off and how that signal can cause the phone to transmit something or turn it on, then the answer has to be no. A trivial solution would be passive RFID (but this is nothing to do with the object being a phone: anything can be tracked if you put a tracking device on it!)
    – matt_black
    Jan 2, 2014 at 13:43
  • I think this is a better question for security.stackexchange.com You're talking about the physical ability of a phone to be compromised by a adverse party. That's out of the scope of Skeptics.SE, imho.
    – Evan Carroll
    Dec 14, 2016 at 2:46

2 Answers 2

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It depends upon your definition of "off", "track", and "phone".

Some phones will keep the baseband chip powered when the device has been shut down. In some cases, security agencies have "updated" the baseband sofware on a large number of phones in order to make them trackable when shut down. It's certainly possible to install OTA updates with almost unlimited abilities on most modern phones, though you would require co-operation from a network, or possibly to run a rogue cell tower.

From an article in Slate:

In 2006, it was reported that the FBI had deployed spyware to infect suspects’ mobile phones and record data even when they were turned off... In 2009, thousands of BlackBerry users in the United Arab Emirates were targeted with spyware that was disguised as a legitimate update. The update drained users’ batteries and was eventually exposed by researchers, who identified that it had apparently been designed by U.S. firm SS8, which sells “lawful interception” tools to help governments conduct surveillance of communications.

With reference to the above article:

According to Gallagher, the NSA may be using mass updates to infect phones of targets overseas (and presumably, any "non-targets" applying the same faux update). This would be difficult, but not impossible, and considering what we've learned about the NSA's far-reaching surveillance net, certainly not implausible.

In summary, the answer is Yes, at least some phones, when they appear to be off, could connecting to a cell tower, and could be tracked to some extent. Given that this article is covering a story from the Washington Post, this is a credible claim.

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    Nice answer. Could you possibly include significant quotes from the sources so we can prevent link rot?
    – Sklivvz
    Jan 2, 2014 at 17:05
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    A sensible definition of "off" is not talking to the cell tower or transmitting RF signals. I'm sure it is possible to put fake software on a phone that pretends to be off but isn't, but then it wouldn't be off. Proving that phone that is really off on this definition can be tracked is going to require a better mechanism (e.g. a proof that an external signal can turn the phone on remotely.) Note that the baseband software can't be running on this definition of off unless it fakes being off (and that can be avoided if a user removes the battery).
    – matt_black
    Jan 3, 2014 at 2:08
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    @matt_black According to the reference cited in this answer, "turned off" is defined as 'the action (verb) which the user thought they had performed on their phone' ... and not the resulting state (adjectival noun) of the phone.
    – ChrisW
    Jan 3, 2014 at 15:10
  • @ChrisW But on this definition the answer is trivial: it is easy to track a phone that communicates with the network; all the NSA has to do is con the user into thinking their phone is off when it isn't. The interesting question is whether a phone that is really off (let's say the battery is out as well) can be tracked.
    – matt_black
    Jan 3, 2014 at 15:16
  • @matt_black Some people were also interested in whether the NSA can find phones after their owners think that they have turned them off.
    – ChrisW
    Jan 3, 2014 at 15:26
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A mobile phone that contains a battery is never fully turned off, otherwise the power button would not work. Having developed cell phones, I can think of two ways to locate an "off" cell phone:

  • Unlikely - passively - any circuit modifies the magnetic fields in which it resides and that effect can be measurable (albeit in a short range, making the technique unpractical).
  • Likely - it is possible (and relatively simple), to modify the phone's software (e.g. using a software "upgrade" or simply by making sure the "option" is included as configurable in the original software) so that it would periodically transmit a traceable signal or signal containing location in the "off" state, record voice or video in the "off" state, etc. This option is useful for targeted tracking, and when done right would have minimal battery draw.

Having said that, I don't think that without modifying the phone as described in the second option above, such surveillance is practical.

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  • Something else you can do by hacking a phone is make it appear to be off: switch off the display and the power-state LED.
    – ChrisW
    Jan 2, 2014 at 10:03
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    Please provide some references to support your claims.
    – Sklivvz
    Jan 2, 2014 at 12:03
  • @EbenezerSklivvze That way all electronics work. If battery is inside the phone and battery is not dead and circuit from battery is not broken the phone is always powered even the screen is black.
    – alex
    Jan 3, 2014 at 15:33
  • @EbenezerSklivvze There is an article in Russian about DIY cellphone GSM-SMS tracker of the how Russian Postal Service Customs work:habrahabr.ru/post/185510 In short: guys used phone's feature to turn on itself once in several hours, send SMS with GPS location, and turn off itself again.
    – alex
    Jan 3, 2014 at 15:44
  • google.com/…
    – alex
    Jan 3, 2014 at 15:53

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