Introduction to Cyber Security

Communicating Securely(Through Voice and Messages) with a Smartphone

1. Secure Voice Communication

Basic telephony
In order to send or receive any calls or communications to your phone, the signal towers nearest you are alerted by your phone of its presence²⁵. As a result of those alerts and communications the network service provider knows the precise geographic location of your mobile phone at any given time.


About Anonymity: If you are conducting sensitive phone conversations or sending sensitive SMS messages, beware of the above tracking 'feature' of all mobile phones. Consider adopting the steps below:

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  Make calls from different locations each time, and choose locations that are not associated with you.
  
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  Keep your phone turned off, with the battery disconnected, go to the chosen location, switch your phone on, communicate, switch the phone off and disconnect the battery. Doing this habitually, each time you have to make a call, will mean that the network cannot track your movements.
  
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  Change phones and SIM cards often. Rotate them between friends or the second-hand market.
  

²⁵ https://securityinabox.org/en/guide/mobile-phones

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  Use unregistered pre-paid SIM cards if this is possible in your area. Avoid paying for a phone or SIM cards using a credit card, which will also create a connection between these items and you.
  

About eavesdropping: Your phone can be set to record and transmit any sounds within the range of its microphone without your knowledge. Some phones can be switched on remotely and brought into action in this way, even when they look as though they are switched off.

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  Never let people whom you don't trust get physical access to your phone; this is a common way of installing spying software on your phone.
  
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  If you are conducting private and important meetings, switch your phone off and disconnect the battery. Or don't carry the phone with you if you can leave it where it will be absolutely safe.
  
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  Make sure that any person with whom you communicate also employs the safeguards described here.
  
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  In addition, don't forget that using a phone in public, or in places that you don't trust, makes you vulnerable to traditional eavesdropping techniques, or to having your phone stolen.