Phone-tapping and listening bugs are methods used for spying. How else does the US National Security Agency (NSA) eavesdrop on its targets?
Elizabeth Law speaks to experts, including Madrid-based security expert Raul Siles, who outline a few common ways phone surveillance can happen and what can be done to secure mobile devices.
Direct to phone
This happens when connecting to an unsecured public network, using Wi-Fi or Bluetooth, which allows anyone to be connected in the network.
On a wireless network, a hacker with the right programme can access one's phone and duplicate the phone's contents or even implant a software that could monitor the phone's activity.
Similarly, this occurs on Bluetooth connections, especially when connecting to an unknown device.
Mobile phones can connect to a network through 2G, 3G and 4G.
In the latter two, which are newer technologies, the phone will try to authenticate the network, ensuring that transmitters really belong to telecommunications companies.
But in the case of a 2G network, a hacker can dupe the phone into "believing" it is connected to a base station (or telephone tower) when it is in fact connected to a hacker's system. This allows them to access information on the phone, eavesdrop and even send messages as the user.
Even on a 3G/4G network, especially in small cities, hackers can create "noise" in the frequency, which forces phones to be on the 2G network, allowing hackers to easily access one's phone.
Some older models of Blackberry smartphones allowed users to be exclusively on a 3G network. But as more users are concerned about battery life, most new models only allow users to turn off the 3/4G function.
One of the solutions is to use Voice over Internet Protocol (VoIP), which allows phone calls and texting to be made through the Internet instead of the public telephone network.
A popular example is Skype. There are also companies offering encrypted voice services, or secured lines for phone calls that cannot be tapped into.
But as more governments are putting pressure on such companies to share their users' information, most have shut down in order to not compromise user privacy.