Wi-Fi networks are being used more frequently every day both in the office and at home but most users give little thought to security.

Anywhere near your home or office someone could be listening in by simply fitting a laptop with a Wi-Fi plug-in. Of course, security can be enhanced by using encryption or other security measures but few people will bother to set them up.

Now, wallpaper that blocks electronic eavesdropping on Wi-Fi traffic but allows radio and mobile phone signals to pass has been developed by BAE Systems.

The big worry has been in the business sector: it takes no time at all for employees to connect up a Wi-Fi base station to a company network. It's a useful addition; the employee can then wander around the office with their laptop while remaining wirelessly connected to the internet for example.

But it is equally easy for an outsider to breach the company's computer security using the Wi-Fi connection.

UK's telecoms regulator, Ofcom, paid BAE Systems to come up with the product as an answer for firms who are becoming increasingly worried about the threat. BAE Systems based its solution on the 'stealth' technology used to hide military radars and radar antennas on warships and aircraft.

Up until now the only solution business had was to make the building into a giant 'Faraday cage' which blocked all frequencies including mobile phones, TV and radio.

The technology, called FSS (Frequency Selective Surface) is supplied in thin sheets made in the same way as printed circuit boards - layers of copper on Kapton polymer and can be applied to any surface including glass windows. They material comes in two varieties: passive, which is effectively permanent, and active, where various areas can be switched on and off to enlarge or limit the area of the network.

You may have to wait awhile to wallpaper your home with the stuff. At the moment it costs some £500 per square metre: Cheap security for big business perhaps but not quite in the price range of your favourite flock fancy.