IMP4GT – A New IMPersonation Attacks in 4G NeTworks Let Hackers To Inject Arbitrary Packets & Break LTE Network Security

Academic researchers discovered a new form of IMPersonation Attacks in 4G LTE networks called IMP4GT allowed attackers to exploit the missing integrity protection for user data and injecting malicious Arbitary packets by impersonating the victims.

4G Long Term Evolution (LTE) is the latest widely deployed mobile communication standard and is used by hundreds of millions of people worldwide for high-speed internet access.

David Rupprecht, Katharina Kohls, Thorsten Holz, and Christina Pöpper, Three Researchers from Ruhr University Bochum & New York University Abu Dhabi, Demonstrate that this new attack breaking the Integrity protection that helps for mutual authentication between the smartphone and the network to verify the identities.

Also, IMP4GT (IMPersonation Attacks in 4G NeTworks) attacks in the LTE network can exploit the reflection mechanism of the IP stack mobile operating system and allowed to inject arbitrary packets and access the payload of existing packets.

IPV4 Protocol in Android and IPV6 in both iOS and Android are vulnerable to IMP4GT attacks and also affected all the LTE enabled devices such as mobile phones, laptops, tablets and more.

Impersonation Attacks Variants

Researchers used two different attack variants in an LTE commercial network to break the mutual authentication and perform the impersonation attacks with the help of open-source LTE Software Stack srsLTE by Software Radio System. 

• Uplink impersonation
• Downlink impersonation

In this Uplink impersonation, the attack allows attackers to impersonation victims towards the networks and use arbitrary IP services such as websites as a victim’s identity.

During the impersonation attack, All traffic generated by the attacker is associated with the victim’s IP address.

“Downlink impersonation allows an attacker to establish a TCP/IP connection to the phone that bypasses any firewall mechanism of the LTE network. The attacker is not able to break any security mechanism above the IP layer.”

As a result, the attacker can bypass any authorization, accounting, or firewall mechanism of the provider. Researchers perform experiments to verify their assumptions and demonstrate the real-world feasibility of IMP4GT in a realistic setup. As a result, they can access a service site that should only be accessible by the user or circumvent the provider’s firewall.

“The attacker can impersonate the victim or the network on the IP layer, which means that it is possible to send and receive IP packets with the stolen identity. However, the attacker cannot access your private mail account or messengers, place phone calls, or break the TLS encryption. We list the consequences for operators, law enforcement, and users as follows. Researchers explained in research paper.

In order to perform this impersonation attack, the Attacker must be highly skilled wit hardware and a customized implementation of the LTE protocol stack and need to be close between the victim phone and LTE relay.

Researchers compare this attack method with IMSI catchers / Stingrays that are successful in ranges of up to approximately 2km. In both of these attacks, the attacker simulates a malicious network towards the victim.

Also “conducting the attack outside a controlled lab environment and without a shielding box would also require more engineering effort.” Researchers said.

This attack affects all the network vendors and all are networks are equally vulnerable and it flaw expected to be fixed in upcoming 5G specification.