The Virtual Dead Drop

April 29th, 2006

I’m fascinated by spy stuff. Dead drops, microfilm dots, tiny cameras, and that kind of stuff fascinate me. I think it stems from my interest in codes, ciphers, and other forms of secret writing. Every time I hear a story about a spy getting caught, I read it, mostly for my interest in the technical tidbits.

Today I read an interesting story about a technique used by the Madrid train bombers to communicate without arousing the interest of authorities. It’s call the Virtual Dead Drop. In spy parlance, a dead drop is a way for a spy to communicate with his handler without meeting, or arousing the suspicion of third parties. For example, in the movie Stalag 17, about life in a Nazi prisoner-of-war camp, the Nazis had a mole amongst the Allied officers. The mole exchanged messages with a Nazi guard by hiding slips of paper inside a hollowed-out chess piece; he then signaled the guard that a message was waiting by tying a loop in the pull-string for the overhead light. The chess piece was the dead drop. (The mole was eventually discovered and… dealt with.)

The Madrid terrorists knew that any email they sent would be immediately detected as it traversed the Internet. So, instead of sending messages from one account to another, the terrorists simply shared one account. They then used the “save draft” feature of their email service to communicate. One terrorist would save a draft with a message for the others; when another terrorist later logged onto the system, he could read the draft, append his reply, and save it again for the first terrorist. The beauty of this technique is that the messages were exchanged without ever having to be sent outside the one account.

What’s interesting about this technique is that I have used it myself… but never thought of it as a dead drop. At work, I have two computers that I use: a Mac and a PC. One day I needed to transfer a file from the PC to the Mac, but I couldn’t get the Mac to connect to the same file server as the PC. Since I couldn’t transfer the file through the file server, I attached it to an email on the PC, then saved a draft of the email. Since the Mac could connect to the email server, all I had to do was open the draft on the Mac and save the attachment to the hard disk.

I never knew what I was doing had subversive uses. I guess I would make a lousy spy.

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