Introduction to Cyber Security

About interception of calls: Typically, encryption of voice communications (and of text messages) that travel through the mobile phone network is relatively weak. There are inexpensive techniques which third parties can use to intercept your written communications, or to listen to your calls, if they are in proximity to the phone and can receive transmissions from it. And of course, mobile phone providers have access to all your voice and text communications. It is currently expensive and/or somewhat technically cumbersome to encrypt phone calls so that even the mobile phone provider can't eavesdrop – however, these tools are expected to become cheaper soon. To deploy the encryption you would first have to install an encryption application on your phone, as well as on the device of the person with whom you plan to communicate. Then you would use this application to send and receive encrypted calls and/or messages. Encryption software is currently only supported on a few models of so-called 'smart' phones.
Conversations between Skype and mobile phones are not encrypted either, since at some point, the signal will move to the mobile network, where encryption is NOT in place²⁶. Using Internet through your Smartphone over mobile data connections or WiFi can provide more secure ways to communicate with people, namely by using VoIP and employing means to secure this channel of communication. Some smartphone tools can even extend some of this security beyond VoIP, to mobile phone calls as well (See Redphone below).


Here we list a few tools and their pros and cons:

Skype

The most popular commercial VoIP application, Skype, is available for all smartphone platforms and works well if your wireless connectivity is reliable. It is less reliable on mobile data connections.

Skype is a non Open-Source software what makes it very difficult to independently confirm its level of security. Additionally, Skype is owned by Microsoft, which has a commercial interest in knowing when you use Skype and from where. Skype also may allow law enforcement agencies retrospective access to all your communications history.

Other VoIP tools

Using VoIP is generally free (or significantly cheaper than mobile phone calls) and leaves few data traces. In fact, a secured VoIP call can be the most secure way to communicate.

RedPhone is a Free and Open-Source Software application that encrypts voice communication data sent between two devices that run this application. It is easy to install and very easy to use, since it integrates itself into your normal dialing and contact scheme. But people you want to talk to also need to install and use RedPhone. For ease of use, RedPhone uses your mobile number as a way to identify you to your contacts. Unfortunately, this makes it more difficult to use RedPhone without a functioning mobile service plan, even on devices capable of using WiFi to connect to the Internet. RedPhone also uses a central server, which puts the administrators of the service in a powerful position by allowing them to see much of the meta-data related to your encrypted VoIP calls.
CSipSimple is a powerful VoIP client for Android phones that is well maintained and comes with many easy set-up wizards for different VoIP services.


²⁶ https://securityinabox.org/en/guide/smartphones