New LTE attacks can reveal accessed websites, direct victims to malicious sites

Three new attacks against the LTE 4G wireless data communications technology have been pinpointed by researchers from Ruhr-University Bochum and New York University Abu Dhabi.

All three target the technology’s data link layer protocols and impair the confidentiality and/or privacy of LTE communication.

The attacks

Two of the attacks are passive and one is active.

“We first present a passive identity mapping attack that matches volatile radio identities to longer lasting network identities, enabling us to identify users within a cell and serving as a stepping stone for follow-up attacks,” the researchers explained.

“Second, we demonstrate how a passive attacker can abuse the resource allocation as a side channel to perform website fingerprinting that enables the attacker to learn the websites a user accessed.”

The third attack, dubbed aLTEr, exploits the fact that LTE user data is encrypted in counter mode (AES-CTR) but not integrity protected, and allows attackers to modify the message payload.

The researchers showed how this attack could be used to perform a DNS spoofing attack to redirect targeted users to a malicious (e.g., phishing) website:

They say that the attacks might require too much effort to be aimed at the general public, but highly resourceful attackers (e.g., attackers backed by nation-states) might deploy them to target people of special interest such as politicians or journalists.

The success of the attacks depend on many things: specialized hardware, a customized implementation of the LTE protocol stack, the attacker being in close proximity to the victim.

“In addition, a controlled environment helps to be successful within an acceptable amount of time,” they noted. “In particular, the use of a shielding box helps to maintain a stable and noise-free connection to the attack setup. Especially the latter cannot be maintained in a real-world situation and more engineering effort is required for real-world attacks.”

More technical details about the attack can be found in the published paper .

What now?

The researchers have notified the GSM Association (GSMA) of their findings earlier this year, and they in turn informed network providers and the 3rd Generation Partnership Project (3GPP), which is the specification body responsible for the development and maintenance of LTE, related 4G standards, and 5G standards.

The researchers have put forward countermeasures for the attacks, but one of them (specification update) is unlikely to be practical, as the implementation of all devices would have to be changed.

Another one involves using correct parameters for HTTPS to prevent the redirection to a malicious website.

Even 5G is not immune to the aLTEr attacks, the researchers pointed out.

“The use of authenticated encryption would prevent the aLTEr attack, which can be achieved through the addition of message authentication codes to user plane packets. However, the current 5G specification does not require this security feature as mandatory, but leaves it as optional configuration parameter.”

5G technology is just beginning to be introduced by cellular network providers and it will take the rest of the world many years to catch up. In the meantime, we’re stuck with the insecure LTE 4G standard.