Computer Security
BitWhisper: Covert Signaling Channel between Air-Gapped Computers using Thermal Manipulations
Researchers demonstrate BitWhisper, a novel bidirectional covert channel that breaches air-gapped computer security using only heat emissions and thermal sensors.
Imagine two computers sitting near each other, both secretly infected with malware, but with absolutely no cables, WiFi, or Bluetooth connecting them—like two people in soundproof rooms who can't talk or send notes. Researchers found a sneaky workaround: computers naturally heat up when they work hard (like when your laptop gets warm during a video game), and they also have built-in thermometers to monitor their own temperature so they don't overheat. The researchers figured out how to make one computer heat up in a specific pattern—like a slow, secret Morse code made of warmth instead of dots and dashes—and the nearby computer's temperature sensor could detect these tiny heat changes and decode the message. It's incredibly slow (only 1-8 bits per hour, meaning it might take an hour to send a single letter), but it's fast enough to sneak out a password or receive a simple command, all without leaving any digital trace that would normally be detected.
- 01
Demonstrates BitWhisper, a bidirectional covert communication channel between air-gapped computers using heat emissions and thermal sensors
- 02
Requires no additional dedicated peripheral hardware, using only built-in CPU/thermal sensors
- 03
Tested across different physical layouts, distances, sensor types, and CPU configurations including virtual machines
- 04
Achieves effective communication at distances of 0-40cm with data rates of 1-8 bits per hour
- 05
Shows feasibility of infiltrating brief commands and exfiltrating small data like passwords via the thermal covert channel
It has been assumed that the physical separation (air-gap) of computers provides a reliable level of security, such that should two adjacent computers become compromised, the covert exchange of data between them would be impossible. In this paper, we demonstrate BitWhisper, a method of bridging the air-gap between adjacent compromised computers by using their heat emissions and built-in thermal sensors to create a covert communication channel. Our method is unique in two respects: it supports bidirectional communication, and it requires no additional dedicated peripheral hardware. We provide experimental results based on implementation of BitWhisper prototype, and examine the channel properties and limitations. Our experiments included different layouts, with computers positioned at varying distances from one another, and several sensor types and CPU configurations (e.g., Virtual Machines). We also discuss signal modulation and communication protocols, showing how BitWhisper can be used for the exchange of data between two computers in a close proximity (at distance of 0-40cm) at an effective rate of 1-8 bits per hour, a rate which makes it possible to infiltrate brief commands and exfiltrate small amount of data (e.g., passwords) over the covert channel.