- The paper demonstrates the feasibility of creating covert acoustical mesh networks between computers in air using ultrasonic audio through speakers and microphones.
- The authors adapted a network stack originally for underwater communication, achieving a data transfer rate of approximately 20 bits per second over almost 20 meters in experiments.
- This work highlights the need for security awareness regarding non-conventional threats and suggests software filters as potential countermeasures against such ultrasonic covert channels.
Covert Acoustical Mesh Networks: An Examination
The exploration of using covert channels to bypass security systems and networks is a profound assessment of how unconventional communication pathways can be employed. This paper presents a convincing argument for using audio modulation in the ultrasonic frequency range to create a covert channel across computing systems via the air medium. By leveraging a network stack originally tailored for underwater communications, the authors demonstrate the feasibility of constructing acoustical mesh networks that are inherently stealthy and capable of multi-hop communications.
The investigation begins by framing covert channels as unintentional communication paths not considered during the design phase of computing systems. The authors exploit speakers and microphones, common peripherals in computers, to send and receive data, thus establishing communication without reliance on traditional network interfaces. This approach is innovative given its focus on ultrasound frequencies, escaping the notice of most security policies that do not typically account for acoustic emissions.
The key strength of this approach lies in the adaptation of a robust underwater communication system to terrestrial applications. The network architecture is divided into several layers, akin to the TCP/IP stack, but custom-designed for acoustic signals, including an application layer, a network layer, an error correction layer, and a physical link layer. Each layer is modular, further contributing to the system's adaptability. The utilization of GUWMANET for ad-hoc routing and GUWAL for tactical messaging ensures efficient packet routing even with limited bandwidth, a crucial adaptation for such a covert setup.
Experimentation involved a multi-laptop arrangement in a purely audio-based mesh network. The authors achieved a transfer rate of approximately 20 bits per second over nearly 20 meters using ultrasonic frequencies. This data transfer, while limited in speed, underscores the feasibility of the concept when integrated into potential threat vectors like remote keylogging through complex mesh setups.
The implications are significant, particularly in challenging existing security paradigms to consider non-conventional threats. The authors propose countermeasures in the form of software-defined audio filters to stymie covert communications, where low-pass filtering can help negate ultrasonic transmissions. Future developments could potentially explore the refinement of real-time detection systems to monitor and neutralize such covert transmissions. The challenge remains to heighten awareness and the scope of security strategies to encompass such stealthy methodologies.
This paper constitutes an important dialogue on security threats posed by physical emanations utilized in covert channels. While initially presented in the context of acoustical mesh networks, the implications extend to broader discussions concerning unconventional security loopholes, demanding adaptive and flexible responses from cybersecurity protocols. Going forward, this exploration could stimulate further inquiry into harnessing varying physical spectra for covert communication, broadening the horizon for both benign and adversarial applications in the AI spectrum.