In 3G networks, the traffic is encrypted from the mobile device, through the Cell Tower to the Radio Network Controller, so both the Radio Access Network and the backhaul portions of the network are ‘notionally’ protected. However if a hacker gains access to the Core Mobile Network, the encryption used for GSM and 3G is ineffective.
- In 2009, hackers computed and published a codebook free on the internet to decrypt calls made over GSM networks
- In 2010, A Practical-Time Attack on the A5/3 Cryptosystem exposed the weakness of the encryption used in 3G GSM Telephony: http://eprint.iacr.org/2010/013.pdf
In 4G networks, the threat is greater as mandated encryption from the Mobile Phone stops at the Cell Tower (eNB), leaving the IP traffic in the backhaul to the operator unprotected.
Mobile Threats are not limited to state-actors or high-cost hackers
With nothing more than a browser, an internet connection and maybe a pre-pay debit card, anyone can spoof SMS messages and Caller IDs. The fact that the receiving mobile number recognizes the and displays their name when the call or text arrives is enough for most individuals to trust the authenticity of the message or call.
Combined with basic social engineering, recipients could give up critical information such as passwords etc. More concerning is where a number of organisation use SMS as an emergency alerting procedure, to evacuate buildings or request the location of an employee.
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