BitWhisper – hacking Air-Gapped PCs through heat emissions

Pierluigi Paganini March 25, 2015

Israeli Researchers have defined a new exfiltration technique dubbed BitWhisper that is based on the heat emissions and built-in thermal sensors.

According researchers at the Ben Gurion University in Israel, by detecting the heat from one computer to an adjacent computer, is possible to establish a channel that can  claiming can facilitate the spread of keys, malicious code and more in general any kind of data.

This sort of bridge between the two computers was dubbed BitWhisper by the researchers  that demonstrated how to exploit it to transfer information between the two air-gapped systems. The channel relies on something so called “thermal pings,” a term used by the researchers to identify the repeated fusion of two networks via proximity and heat.

The BitWhisper attack is very complex, but it is very interesting because it doesn’t require any dedicated or modified hardware.


The researchers involved in the experiment are Researchers Mordechai Guri, Matan Munitz and the professor Yuval Elovici, the three experts plan to publish a paper, entitled “BitWhisper: Covert Signaling Channel between Air-Gapped Computers Using Thermal Manipulations,” describing the BitWhisper technique and findings of their experiment.

“At this stage, the attacker can communicate with the formerly isolated network, issuing commands and receiving responses,” states the report.

The researchers placed two computers at up to 15 inches from each other, they tried to transmit up to 8 bits of data per hour, an amount of information that could be enough to steal sensitive data like user’s credentials and secret keys, or to send commands to any agent listening on the target machine.

An Air-gapped network still represent a stringent security measure when it is necessary to isolate a system from the Internet to preserve it and the data it manages, typical applications are military networks and industrial control systems architectures.

Unfortunately a persistent attacker could by pass the security measure in different ways, by infecting a network with a USB key, like happened to the Stuxnet virus or the Fanny tool used by the Equation Group APT).

On October 2014, Israeli researchers demonstrated how to hack air gapped networks by using other techniques. One research relied on an all-in-one printer, complete with a built-in scanner, to infiltrate an air-gapped network, or a system, and steal sensitive data. The experts demonstrated that it is possible to compromise air-gapped networks controlling the malware with a long-distance laser which could be installed on a drone.

Early 2014, a group of researcher at Ben Gurion University demonstrated how to infect machines in air gapped networks through a cell phone and use the mobile device as an attack vector to hit the computer in the vicinity.

The BitWhisper bridge allows to establish a bidirectional communication channel between two computers by using the heat emitted by various internal components. The experts explained that in order to compromise the machine it is sufficient to infect the machine in the air-gappep network with a malware.

“BitWhisper provides a feasible covert channel, suitable for delivering command and control (C&C) messages, and leaking short chunks of sensitive data such as passwords,” continues the paper. 

In their experimental scenario, the researchers placed two computers parallel to each, one of the machines was connected to the Internet and the other was connected to the air-gapped network.

Hypothesizing that a malicious code was installed on both computers, on sender-end the heat generated by internal component workload (i.e. CPU, GPU) is transferred to the recipient which monitors the changes in temperature.

“BitWhisper establishes a covert channel by emitting heat from one PC to the other in a controlled manner. By regulating the heating patterns, binary data is modulated into thermal signals. In turn, the adjacent PC uses its built-in thermal sensors to measure the environmental changes. These changes are then sampled, processed, and demodulated into binary data,” explained the researchers.

Below the BitWhisper video proof of concept.


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Pierluigi Paganini

(Security Affairs –  BitWhisper,   air-gapped network)

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