Introduction

Air-gapped systems—computers or networks that are physically isolated from unsecured networks like the internet—are often considered a last line of defense. They’re used in environments where data sensitivity or operational security is paramount. But despite the perceived security of these isolated systems, there is a growing list of malware strains that have successfully breached air gaps using creative and unconventional methods. Below is an overview of real-world examples that demonstrate how attackers have managed to bypass air gaps—along with the specific techniques used.

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Stuxnet

Year: 2010
Target: Iranian nuclear facilities (Natanz)
Purpose: Industrial sabotage

How it crossed the air gap:

• Delivered via infected USB drives.
• Exploited multiple zero-day vulnerabilities to spread inside the network.
• Specifically targeted Siemens Step7 PLCs used in centrifuge control systems.

Remarks:
Stuxnet was one of the first publicly known cyber weapons to successfully cross an air gap and cause physical damage. It’s widely believed to have been developed by state-sponsored actors.

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Ramsay Framework

Year: Discovered in 2020
Target: High-value, air-gapped environments
Purpose: Document harvesting and exfiltration

How it crossed the air gap:

• Propagates via USB drives and network shares.
• Exploits vulnerabilities in Microsoft Office (e.g., CVE-2017-0199 and CVE-2017-11882).
• Gathers sensitive documents (Word, PDF, etc.) for later staged exfiltration.

Remarks:
Ramsay demonstrates that attackers can prepare malware to quietly operate within isolated systems over long periods, especially when removable media is part of the operational workflow.

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GoldenJackal

Year: Publicly reported in 2024
Target: European government systems
Purpose: Espionage

How it crossed the air gap:

• Delivered via custom USB worms, potentially through supply chain or insider access.
• Collected sensitive documents, encryption keys, and emails.
• Details on exfiltration remain classified, though removable media and possibly RF-based transmission are suspected.

Remarks:
GoldenJackal illustrates how sophisticated actors can build bespoke toolchains for specific, high-security environments.

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PixHell and Fansmitter

Target: Desktop and server-class systems with acoustic or visual peripherals
Purpose: Covert data exfiltration

How they crossed the air gap:

PixHell:

• Uses modulated brightness patterns on LCD screens to generate high-frequency acoustic signals.
• These signals are then picked up by nearby microphones on smartphones or laptops.

Fansmitter:

• Modulates CPU workloads to control fan speed and emit acoustic signals.
• These patterns can be interpreted by nearby microphones as binary data.

Remarks:
Both attacks rely on components not traditionally considered security risks—monitors and fans—turning them into unintentional transmission devices.

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PowerHammer

Year: 2018
Target: Desktop PCs in secured environments
Purpose: Data exfiltration via power lines

How it crossed the air gap:

• Malware on the target system varies CPU workload to create specific power fluctuations.
• These fluctuations are detectable on power lines connected to the system and can be decoded externally.

Remarks:
PowerHammer highlights that even power infrastructure can act as a data transmission medium if the attacker controls the endpoint.

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AirHopper and LANTENNA

Purpose: Electromagnetic-based data exfiltration

AirHopper:

• Uses the video card to emit radio signals via the display cable.
• Mobile phones with FM radio receivers can detect the signal within a few meters.

LANTENNA:

• Utilizes Ethernet cables to emit RF signals by manipulating the data bus.
• The emitted RF can be received using AM radio antennas.

Remarks:
These techniques demonstrate how electromagnetic leakage can be intentionally exploited to cross network boundaries.

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BadBIOS (Alleged)

Year: Reported in 2013
Target: Multi-platform environments
Purpose: Unknown (likely espionage)

How it allegedly crossed the air gap:

• Claimed to use ultrasonic transmissions between systems via built-in speakers and microphones.
• Also allegedly used firmware persistence mechanisms.

Remarks:
While unverified and controversial, the BadBIOS story led to further academic research into ultrasonic data transfer and BIOS-level implants.

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Conclusion

Air-gapped systems provide strong baseline protection, but they are not impenetrable. Many successful breaches have relied on physical access, compromised removable media, or even emissions that weren’t originally considered security-relevant (like sound or EM waves). Organizations operating air-gapped environments must consider the full spectrum of attack surfaces—including power supplies, peripherals, and human behavior—and implement rigorous security controls beyond software firewalls and physical disconnection.

Some defensive measures include:

• Strict control over USB and removable media.
• Disabling or physically removing unused audio, RF, and video components.
• Using electromagnetic shielding and power-line filters.
• Deploying anomaly detection systems for non-networked endpoints.

Air gaps are just one part of a layered security model. In a world of increasingly creative adversaries, they are a necessary—but no longer sufficient—barrier.