Bogus signals send sat navs astray

GPS systems can be subverted using false signals generated by a transmitter in a box the size of a briefcase, researchers have warned.

They point out that sat nav is used for a proliferating number of critical applications, including power grids and tagged offenders, that lack the security features of military systems.

The researchers from Cornell and Virginia Tech discovered the vulnerability when they were investigating the effects of solar flares on GPS satellites, according to a report in MIT Technology Review.

Professor Richard Langley, a GPS specialist at Canada's New Brunswick University, told the magazine that the issue had been known about for years but little had been done about it. He added: "You'd think more would have been developed by now."

One option would be use multiple antennas revealing that bogus signals have a single source.

The problem does at least establish a raison d'etre for Galileo, the controversial European GPS satellite system due to go live in 2013. It provides civilians with encrypted signals.