Security Experts:

Researchers Devise New Attacks Against 4G LTE Mobile Networks

A team of researchers from Purdue University and the University of Iowa have discovered 10 new attacks against the 4G LTE protocol, which could allow adversaries snoop on messages, deny service, and even track the location of users.

In a whitepaper (PDF), the team provides information on LTEInspector, the adversarial model-based testing approach they decided to adopt in this quest, and on the 10 new vulnerabilities they discovered in the protocol, alongside 9 previously known attacks. 

LTEInspector, the researchers explain, was designed to analyze three critical procedures in the 4G LTE network, namely attach, detach, and paging. Designed to be tool-agnostic, the new approach can be “instantiated through any generic symbolic model checker and cryptographic protocol verifier,” the researchers say. 

Using the new approach, the researchers discovered undocumented attacks on each of the critical procedures in the protocol. Four of the attacks affect the attach procedure, one affects the detach procedure, and five affect paging. 

The first such attack is called Authentication Synchronization Failure and could disrupt the attach procedure, thus resulting in the victim experiencing service disruption. 

A Traceability Attack can be abused to track a particular victim user equipment. “This attack can also be performed for a specific user with only the knowledge of victim’s phone number,” the researchers say. 

The Numb Attack allows the adversary to inject an out-of-sequence control-plane protocol message and disrupt the service of a victim user device until restart. This issue can be chained with other types of assaults to impersonate the victim. 

A Paging Channel Hijacking attack enables an adversary to hijack the victim device’s paging channel, thus preventing it from receiving legitimate paging messages, meaning that the victim does not receive service notifications such as incoming phone calls or SMS. 

A Stealthy kicking-off Attack results in the user device disconnecting from the Evolved Packet Core (EPC) and can be used as a prerequisite of the Authentication Relay Attack.

As part of a Panic Attack, an adversary injects fake emergency paging messages to a large number of user devices, thus creating artificial emergency. 

An adversary could also launch Energy Depletion Attacks to make user devices “perform expensive cryptographic operations,” by forcing them to repeatedly carry out the expensive attach procedure. 

The Linkability Attack, the researchers say, would allow an adversary to trace a victim device in a cell area by broadcasting a paging with the victim’s IMSI and observing the received attach request. 

The only attack against the detach procedure is the Detach/Downgrade Attack, where the adversary injects network initiated detach requests to disrupt the victim’s service. 

The researchers also point out that it is possible to chain some of these attacks with previously known assault methods, as well as among them, which could have wider implications. One such attack is the Authentication Relay Attack, where the victim device is disconnected from the EPC and the adversary connects instead, impersonating it, despite the lack of proper credentials. 

“In this attack the adversary, however, cannot decrypt or inject valid encrypted messages unless the operator uses a weak or no security context,” the researchers explain. 

Related: Mobile Ecosystem Vulnerable Despite Security Improvements: DHS

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