GPS jammers are threatening shipping, a conference in the UK has been warned.
Through a monitoring program called Sentinel - SErvices Needing Trust In Navigation, Electronics, Location & timing - it's been established that the devices are being widely used on British roads.
And, say the project's organisers, there are implications for the shipping industry, and even global financial trading.
"Today's evidence from roadside monitoring shows that we have moved on from a potentially threatening situation to a real danger that we must address now," says Bob Cockshott, director of position, navigation and timing at the ICT Knowledge Transfer Network and organiser of the GNSS Vulnerability 2012 conference.
"With the reliance on GPS systems in the maritime environment, highlighted by the General Lighthouse Authority, our vulnerability on land and at sea should not be underestimated."
Through the Sentinel project, jamming monitors were placed at around 20 locations in the UK - and at one, over 60 individual jamming incidents were recorded in a six-month period.
The jammers are believed to be used mainly by people in cars equipped with tracking devices to disguise their whereabouts.
But according to the Sentinel team, there's a danger that the same $80 devices could be used to disrupt shipping.
In tests, they've been shown to make ships veer off course without the crew's knowledge and give out false information to other ships about their position – significantly increasing the likelihood of a collision.
They can also cause communications channels to fail, along with the emergency service system which sends out alarms and guides rescuers.
"Whilst we expected some disturbance to the ship's chart display, this research revealed four or five other systems, all reliant on GPS which failed," says consultant and location and timing system expert, Professor David Last.
"The spread of the jamming technology used in these trials, with devices available online for only £50, makes a major incident at sea, whether accidental or intentional, a real danger. In the English Channel, the world's busiest seaway, I personally believe we will see such an incident in the next decade."
At least as dangerous, the conference will hear today, is the spoofing of navigation systems. Spoofing generates false GPS signals to alter user's perceptions of time and location, and can be undetectable and virtually untraceable.
"So far no credible high profile attack has been recorded but we are seeing evidence of basic spoofing, likely carried out by rogue individuals or small groups," says Todd Humpheys from the University of Texas - owner of the world's most powerful civil GPS spoofer.
"Whilst the leap to more advanced, untraceable spoofing is large, so are the rewards. It's therefore guaranteed that criminals are looking at this. All it takes is one person to put one together and publish it online and we have a major problem."
One sector at risk, perhaps surprisingly, is high-frequency financial trading. Criminals could throw off the GPS timing systems that time-stamp financial trades, in a process known as 'Time Sabotage'.
Even a few milliseconds' discrepancy could create confusion, benefiting unscrupulous traders.