What is Air Gap?
A security measure that physically isolates a computer or network from the internet and other unsecured networks. An air-gapped system has no wired or wireless connections to the outside world, making remote hacking virtually impossible.
Also known as: Air-Gapped, Air Wall
An air gap is the ultimate network security measure: complete physical isolation from the internet. If there's no connection, there's no remote attack vector.
Use Cases
Cryptocurrency Cold Storage
- Private keys stored on offline computer
- Transactions signed offline, broadcast separately
- Immune to remote wallet theft
Highly Sensitive Data
- Government classified systems
- Critical infrastructure controls
- Medical research data
Secure Key Generation
- Creating cryptographic keys
- Generating master passwords
- Setting up hardware wallets
True Air Gap Requirements
- No network interfaces: WiFi, Ethernet, Bluetooth all disabled/removed
- No wireless peripherals: Wired keyboard and mouse only
- No removable media reuse: USB drives don't go back to connected systems
- Physical security: Locked room, limited access
- Faraday consideration: For extreme cases, block electromagnetic emanations
Bridging the Air Gap
Data transfer to/from air-gapped systems requires careful protocols:
- One-way transfers: Data in via optical media, verified before use
- QR codes: For small data like transaction signatures
- Dedicated transfer machines: Never connect to both networks
Attacks Against Air Gaps
Sophisticated attackers have breached air gaps using:
- USB malware: Stuxnet famously jumped air gaps via USB
- Acoustic signals: Data encoded in sounds
- Electromagnetic emissions: Reading data from screen flicker
- Power line analysis: Detecting activity through power consumption
Practical Air Gapping
For most users, a practical "soft" air gap:
- Old laptop with WiFi hardware removed
- Fresh OS install, never connected to internet
- Use for sensitive operations only
- Transfer data via encrypted USB, used nowhere else
Related Terms
Cold Storage
Keeping cryptographic keys or digital assets offline, disconnected from the internet. Cold storage prioritizes security over convenience—keys can't be hacked remotely because they're not connected to any network.
Offline Security
Protecting data and systems that are not connected to the internet. Offline security addresses physical access, device theft, and local attacks. When data never touches a network, it can't be hacked remotely—but it can be stolen, seized, or compromised in person.
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