Technology in terms you understand. Sign up for the Confident Computing newsletter for weekly solutions to make your life easier. Click here and get The Ask Leo! Guide to Staying Safe on the Internet — FREE Edition as my thank you for subscribing!

Can my mobile phone calls be listened to?


I crossed paths with someone who I believe is a bad person in a professional
setting and I’m afraid that they know that I know something. Do you know if
it’s possible for somebody to listen to my cell phone conversations remotely?
I’ve never used the phone for internet and nobody has physical [access] to the device
but me and I do not use Bluetooth. It’s a Boost mobile phone. I don’t expect
that you’ll have time to answer this especially because it’s not directly a
computer a question, but if you do, please don’t include any identifying

In this excerpt from
Answercast #60
, I look at the problems and possibilities of eavesdropping in
on cellular phone calls.

Become a Patron of Ask Leo! and go ad-free!

Cell phone snoops

Well, OK, no identifying information included other than the fact that you
have a Boost phone.

So the short answer is yes and no.

Here’s the problem. First of all, old analog phones (which I believe are
actually no longer supported by the network) – absolutely! They could be
listened to. They are simply radios and radios can be listened to with the
proper equipment.

These days, all of our mobile phones are digital. Even when we’re not using
mobile data, the actual phone calls we make are converted to digital data.

Calls are encrypted

That digital data, as it turns out, is indeed encrypted. The intent is that
the data cannot be eavesdropped on as it’s transmitted over the air because
it is still fundamentally a radio and anybody with a radio tuned to the right
frequency could technically listen into the data.

That’s why encryption is important.

Now, here’s the bad news: the encryption standard for most of our digital
phones these days is so old that it is designed to work with very, very weak
hardware: what today we would consider to be very, very underpowered

What that means is that even though it’s encrypted, it’s actually not that
hard to decrypt. The algorithms aren’t that strong and the amount of processing
power that it takes to decrypt a telephone call these days isn’t really that

Equipment and range

Now, to go back to some good news here, it does take special equipment. So
someone would actually have to have a specific intent to go out and start
eavesdropping on cellular phones in order to be able to eavesdrop on your
phone. And yes, they would need to be within range; within radio range of your

So, consider what the range of a phone is. In line of sight, it’s what? A
mile, two miles? Whatever the distance is to your cellular towers that it’s
connecting to.

So the chances of somebody actually going through the effort (even though
it’s not computationally expensive)… the chances of someone getting the
specialized equipment to be able to do this, setting up the software to be able
to decrypt what it captures – that’s not really that common. It’s not something
that I worry about very much at all.

If you are of course the target of somebody who has the ability, who has
the resources, who has the desire, who has the whatever, to do this, then yes,
it’s certainly possible.

Cell phone privacy

I certainly wouldn’t consider a digital phone call to be private for
example from (I don’t know…) intelligence agencies worldwide. The encryption
just isn’t that strong. You’d probably want to layer some other kind of
encryption on top of it.

But the short answer is that while it’s possible that cellular telephone
calls can in fact be listened in on, it is difficult enough that it is just one
of those things where somebody would really have to go out of their
way for it to happen.

That’s unlike wireless networking or Wi-Fi – where anybody with a laptop
basically has everything they need to listen in to an open Wi-Fi conversation.
All they need is some software and the software is available for free.

When you go to things like cellular phones, digital cellular phones, you
need specialized hardware, you need specialized software that most people
don’t have – and to be honest, I wouldn’t even know where to start to go get

Do this

Subscribe to Confident Computing! Less frustration and more confidence, solutions, answers, and tips in your inbox every week.

I'll see you there!

3 comments on “Can my mobile phone calls be listened to?”

  1. I’m not any expert on cell phones, but for your info it is not hard to hear persons calls. I recently bought a set of stereo head phones, Sony, to listen to my living room tv as my wife complains its too loud. The Sony headset is TMR-RF970R and it says it is a RF Stero Transmitter. (e.g. the
    headphones connect wirelessly to transmitter connected to the tv.) One morning, crystal clear, my headset picked up the neighbor, talking on her cell phone or maybe her portable phone. The Sony headset has a switch for 1,2, or 3 channels on the 2.4 gighertz channel… I never investigated further as I set up tv channel, but at the time, I had no trouble hearing her conversation. I am 30 ft from her condo and just a concrete wall dividing us. I am writing this becsause you were quite explicit in saying its not “easy” to capture phone conversation; with this wireless headset, it was very easy to pick up the conversation.

    That’s not a cellular/mobile phone you heard. Cell phones all transmit digital data these days which would not be intelligible on headsets as you describe. More likely a simple cordless home phone, which does operate in the 2.4ghz range.

  2. John, there is a world of difference between a cell phone and a cordless phone. Leo was talking about current cell phones. Cordless phones vary from manufacturer to manufacturer, and may be no more than an analog radio, just like the old cell phones Leo mentioned. While many cordless phones nowadays are digital and encrypted, nothing requires them to be as such, since all that’s required is that they talk to the appropriate base unit. (And, apparently, the Sony headset you mention is also unencrypted analog as well.)

  3. I’d like to add to my previous comment; I checked with my neighbor and the phone I listened into was not digital, it was their cordless 2.4 ghzy phone. Sorry, it was not digital.


Leave a reply:

Before commenting please:

  • Read the article.
  • Comment on the article.
  • No personal information.
  • No spam.

Comments violating those rules will be removed. Comments that don't add value will be removed, including off-topic or content-free comments, or comments that look even a little bit like spam. All comments containing links and certain keywords will be moderated before publication.

I want comments to be valuable for everyone, including those who come later and take the time to read.