As usual for Schneier’s blog, the comments are at least as interesting as the article.
I haven’t blogged on infosec in a while (true, I haven’t blogged in a while, but I was out all last week on ‘vacation’ sweating my ass off in preparation for our July 4th party (which went very well indeed!)), because of my job I have to be careful and decided it would be better to avoid the topic. However, this one appears safe. It is interesting that these sorts of emanations are detectable at even this distance, I would think there would be so much inadvertent shielding and noise that you would have to put a detector directly on the laptop to get the data. TEMPEST has always been interesting to me, though I only discovered it by accident when I was looking around for the Tempest video game (one of my favorites, by far; I have avoided trying to purchase a refurbished unit because I would probably spend all day playing and have other things I need to do). In the old CRT days you could have a van parked in a parking lot a goodly distance away and be able to recreate the screen image (with appropriate equipment, of course) and it was interesting when people created fonts that would defeat such attempts. I am sure TEMPEST is alive and well, but defense against these sorts of things is relatively easy: just put a bunch of distance between yourself and any potential adversaries. The inverse square law is unyielding in its power and, as the above article shows, inches matter.