A group of academic researchers have revealed a design weakness in the 4G/5G protocol which can be exploited by an attacker to identify the victim’s presence in a particular cell area just from the victim’s soft-identity such as phone number and Twitter handle. “Any person with a little knowledge of cellular paging protocols can carry out this attack,” said Syed Rafiul Hussain, one of the co-authors of the paper, told TechCrunch.

The abstract below from the paper released today called “Privacy Attacks to the 4G and 5G Cellular Paging Protocols Using Side Channel Information” specifies the dangers of the discovered vulnerability.

“The cellular paging (broadcast) protocol strives to balance between a cellular device’s energy consumption and quality-of-service by allowing the device to only periodically poll for pending services in its idle, low-power state. For a given cellular device and serving network, the exact time periods when the device polls for services (called the paging occasion) are fixed by design in the 4G/5G cellular protocol. In this paper, we show that the fixed nature of paging occasions can be exploited by an adversary in the vicinity of a victim to associate the victim’s softidentity (e.g., phone number, Twitter handle) with its paging occasion, with only a modest cost, through an attack dubbed ToRPEDO. Consequently, ToRPEDO can enable an adversary to verify a victim’s coarse-grained location information, inject fabricated paging messages, and mount denial-of-service attacks. We also demonstrate that, in 4G and 5G, it is plausible for an adversary to retrieve a victim device’s persistent identity (i.e., IMSI) with a brute-force IMSI-Cracking attack while using ToRPEDO as an attack sub-step. Our further investigation on 4G paging protocol deployments also identified an implementation oversight of several network providers which enables the adversary to launch an attack, named PIERCER, for associating a victim’s phone number with its IMSI; subsequently allowing targeted user location tracking. All of our attacks have been validated and evaluated in the wild using commodity hardware and software. We finally discuss potential countermeasures against the presented attacks.”