So I found an interesting note in an article by Bruce Schneier on air-gapped computers:
Note: the first company to market a USB stick with a light that indicates a write operation -- not read or write; I've got one of those -- wins a prize.
Since Globotron happens to make USB firewalls with independent software-controlled LEDs, and since I happen to have the source code in front of me... challenge accepted!
The LEDs in question were previously used to indicate error conditions, red for the Upstream processor and yellow for the Downstream. But there's no reason we can't put them to further use here.
A typical session with the Armadillo firewall reading and writing simultaneously looks like this. Yellow blinky means device reads, and red blinky means device writes:
This feature turns out to provide real insight into how the computer is accessing the storage device. Attach an NTFS volume to Windows and watch the cascade of write operations as the Explorer window pops open. Delete a file on Linux and watch precisely nothing happen... until the cache flushes 10 seconds later.
It makes a great complement to the Armadillo's read-only mode for your offline or air-gapped systems. And even on the USG which can only be set to read-only mode by compiling modified firmware, it gives the user a level of insight that can't be found anywhere else.
So from today every Armadillo and USG firewall that ships from the store will be programmed with extra blinky. And for those following along at home, the latest open-source builds (r05) also have the feature enabled. You can even customize the build (say if you want blinks on writes only).
Now all that is said, only one question remains: Bruce, what's the prize?