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You're assuming that the only way to compromise a computer is through a direct internet connection. This is wrong. Pre-internet viruses spread on diskettes. Th

You're assuming that the only way to compromise a computer is through a direct internet connection. This is wrong. Pre-internet viruses spread on diskettes. The point of the air gap is to assume that any computer that has ever been connected to the internet is infected in an undetectable manner and that this infection is capable of spreading autonomously. Only by physically denying the infection the means to spread can you protect against it. Secondarily, you want to deny the infection the means to communicate back home, but sometimes the point of an infection isn't to steal data - see Stuxnet.

notacoward 13y ago
"You're assuming that the only way to compromise a computer is through a direct internet connection." I'm assuming the exact opposite. I recognize, as does Schneier, that infection can occur without such a connection. Any mechanism that facilitates transfer of data also facilitates infection. That includes USB sticks and CD-Rs, which have the additional problem of leaving artifacts around for others to pick up later. It's the "we can secure USB sticks better than we can secure networks" belief that's magical. "Only by physically denying the infection the means to spread can you protect against it." As soon as you physically move a USB stick from one machine to another, you've effectively created a network. A really crappy one with high latency, but that doesn't make it any more secure as you yourself illustrate with the diskette example.
- mseebach 13y ago
  A network connection, even brief has an enormous attack surface. The corresponding surface when using physical media is much smaller.
  - notacoward 13y ago
    Bull. A network connection on a physically separate network subject to proper inspection/monitoring has a very small attack surface. The corresponding attack surface for a USB stick is larger, with new exploits being discovered every day. The separate switch is functionally identical to the USB stick. They both allow transfer of data. They can both potentially be attack vectors. They both (in this construction) require manual intervention to complete the data path. The only difference is that it's a lot easier to get a copy of someone's data on a USB stick, after someone conveniently recorded their data transfer on a readily purloined bit of media. You can't acknowledge the exploits that have occurred via diskettes or USB sticks, and then also say they're fundamentally better than an isolated network. It's illogical. In fact, it's stupid.

notacoward 13y ago

"You're assuming that the only way to compromise a computer is through a direct internet connection." I'm assuming the exact opposite. I recognize, as does Schneier, that infection can occur without such a connection. Any mechanism that facilitates transfer of data also facilitates infection. That includes USB sticks and CD-Rs, which have the additional problem of leaving artifacts around for others to pick up later. It's the "we can secure USB sticks better than we can secure networks" belief that's magical. "Only by physically denying the infection the means to spread can you protect against it." As soon as you physically move a USB stick from one machine to another, you've effectively created a network. A really crappy one with high latency, but that doesn't make it any more secure as you yourself illustrate with the diskette example.

mseebach 13y ago
A network connection, even brief has an enormous attack surface. The corresponding surface when using physical media is much smaller.
- notacoward 13y ago
  Bull. A network connection on a physically separate network subject to proper inspection/monitoring has a very small attack surface. The corresponding attack surface for a USB stick is larger, with new exploits being discovered every day. The separate switch is functionally identical to the USB stick. They both allow transfer of data. They can both potentially be attack vectors. They both (in this construction) require manual intervention to complete the data path. The only difference is that it's a lot easier to get a copy of someone's data on a USB stick, after someone conveniently recorded their data transfer on a readily purloined bit of media. You can't acknowledge the exploits that have occurred via diskettes or USB sticks, and then also say they're fundamentally better than an isolated network. It's illogical. In fact, it's stupid.