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upstart writes in with an IRC submission:

New Attack Lets Hackers Decrypt VoLTE Encryption to Spy on Phone Calls:

A team of academic researchers—who previously made the headlines earlier this year for uncovering severe security issues in the 4G LTE and 5G networks—today presented a new attack called 'ReVoLTE,' that could let remote attackers break the encryption used by VoLTE voice calls and spy on targeted phone calls.

The attack doesn't exploit any flaw in the Voice over LTE (VoLTE) protocol; instead, it leverages weak implementation of the LTE mobile network by most telecommunication providers in practice, allowing an attacker to eavesdrop on the encrypted phone calls made by targeted victims.

VoLTE or Voice over Long Term Evolution protocol is a standard high-speed wireless communication for mobile phones and data terminals, including Internet of things (IoT) devices and wearables, deploying 4G LTE radio access technology.

The crux of the problem is that most mobile operators often use the same keystream for two subsequent calls within one radio connection to encrypt the voice data between the phone and the same base station, i.e., mobile phone tower.

[...] To initiate this attack, the attacker must be connected to the same base station as the victim and place a downlink sniffer to monitor and record a 'targeted call' made by the victim to someone else that needs to be decrypted later, as part of the first phase of ReVoLTE attack.

Once the victim hangs up the 'targeted call,' the attacker is required to call the victim, usually within 10 seconds immediately, which would force the vulnerable network into initiating a new call between victim and attacker on the same radio connection as used by previous targeted call.

Also at: Threatpost.

Original Submission