How not to be seen

For a while, things weren't too bad. You could have a microphone in your suspect's office and run wires to your listening post, or you could try and hide a radio transmitter nearby -- but the combination of huge valves and crude transmitter technology made such exercises easy to detect. Along came the transistor, which shrank bugs to the size of a broad bean, and the spies were very happy. But not as happy as when integrated circuits arrived -- not only could you make surveillance equipment as small as you liked, you could build in masking techniques that rendered them very hard to detect. A basic bug needs but two transistors: with modern chips packing upwards of a billion on each sliver of silicon, the only limit to surveillance technology is the imagination of the spies and their ability to physically place the devices.

Even those ideas are out of date. Looking around my desk, I can see five devices that have microphones built in and attached to complex electronic circuitry. Three of them also have radio transmitters -- a mobile phone, a cordless phone, and a Wi-Fi laptop -- while the desktop computer is linked to the Internet via a permanent broadband connection. Any of these could be compromised by the addition of a tiny amount of software and made to relay everything in earshot to anywhere in the world: I even take two of them with me wherever I go. And in fact, there's no need for MI5 to go to even that much bother: like most of us, nearly everything of interest that I do is reflected in some way by my phone calls, emails and online activities.

It's here that most espionage takes place, in our day-to-day use of IT equipment. The spies do have the use of tons of special space hardware with codenames like Lacrosse and Crystal, taking pictures and listening to every radio transmission they can, but unless you're using a walkie-talkie in the Hindu Kush, there are much easier ways for what you say and do to reach the eyes and ears of those who care.