What can be done to bridge the Air Gap, except autorun?

Is there any hardware butterflies that can attack physically isolated Unix/Linux machine in common usb drives, like VSC (Vendor Specific Commands)?



Any bug in the handling of USB devices can be exploited by malicious hardware. That's how the PS3 Jailbreak worked.

Remember that when you plug a "USB Flash drive" in a machine, you cannot be sure that what you plug is really "just a Flash drive". The machine sees it as a "USB device" which may claim to be a keyboard, a mouse, a network interface... A malicious Flash drive could be in fact a wireless network device, which claims to be some sort of ethernet card; the machine may react by automatically connecting to it (DHCP and so on): no more air gap !

Alternatively, the USB device may claim to be a USB-to-firewire converter and the device driver, already known to the machine, would then grant device-initiated DMA privileges: the device can then read and write any data byte in the machine.

Really, if you are serious about your security, don't plug untrusted device in a USB port.

  • Did you mean that better use CD/DVD disc? – trankvilezator Sep 20 '13 at 16:28
  • 3
    Indeed, a CD would be better, since a CD-ROM reader won't use it in any way other than reading bytes. A CD won't be able to masquerade as another kind of device. As you have noticed, beware of any Autorun features, of course. – Thomas Pornin Sep 20 '13 at 16:44
  • Great, I'll not put you answer as completed, but anyway thank you very much. Still waiting for more informative instructions to bridge air gap. – trankvilezator Sep 30 '13 at 15:18
  • See, Schneier builds his own air gap. Comments are pretty. schneier.com/blog/archives/2013/10/air_gaps.html – trankvilezator Oct 23 '13 at 15:06

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