Transcript

security but if I try and go deeper into the computer the data will be encoded so all I'll get back is this sort of information what's known as shash to be able to read that I'd need to have access to a decoding system but we found out about a particularly worrying method of eavesdropping that gets round even the most advanced encryption procedures by reading the operators screen before it's encoded the way of doing that is based on a phenomenon that's been known about for at least 20 years and although it's not actually an official secret there was no one in this country who was prepared to talk to us about it the phenomenon is quite simply that all electrical equipment gives off signals if you take even a pocket calculator and you put it near to a radio which has long way on it you can hear the interference as I press the piece well even if a calculator radiates a signal like that you might still be surprised to learn that a computer terminal radiates a signal that can be picked up over two miles away what's more that signal carries the information displayed on the terminal screen and that information can be read the data on this video screen is being transmitted all around the studio and it's being picked up by this receiving system here that's not linked to it in any way at all it's only a hundred pounds worth of equipment so it's not the greatest picture and i'll try and stabilize it a bit there and if i move the aerial you can see that the information disappears off the screen move it back and it returns now all we've got here is an ordinary television set with an aerial and an amplifier and a rather special if cheap box of tricks but we had to go to the doctor near laboratories in holland to get hold of it and cement lee they use this equipment quite legally to investigate this very problem and they were the only people you'll excuse me who we knew who could find out and would admit to having it well we've seen it working in the controlled conditions of the studio but yesterday we set this up to see how it would work outside at the moment we're outside an office block in West London and we found that there's a video screen operating about halfway up the building probably on the seventh or eighth floor and in fact it's a letter being typed out on that screen I can actually read it here it says dear mr. Jackson thank you for your groups thank you for your letter requesting views whoop of mustard again requesting the use of our facilities I have spoken to mr. Saunders and he agrees that there may well be problems finding a parking space on the day of your visit and the letter goes on I would think it was fair to assume that this is a word processor but of course it could be something far more confidential now the picture is just readable it's hardly perfect but more money and poor determination would soon improve that so is there any way to stop this well yes there is you can cover your terminal and your screen with a metal screen and it'll also cover the front here with glass perhaps with a mesh inside it if you know that you'll do some good by absorbing the signals and conducting them down to earth but there will still be other leaks and to make it 100 percent effective this screening will be have to be made to a very high specification called Tempest and that's the standard used by the government Defense Department's but tempers protection would quadruple the cost of an average computer terminal so most business computers like those that all branches of your bank will be left vulnerable but before you rush out to close down your account we must point out that we believe that there are only a very few people outside government departments who know how to do it and having said that the very fact that we were able to gain access to computer information with very primitive equipment must give cause for concern