LAS VEGAS, Aug 10 (Reuters) - A recent surge in GPS

"spoofing", a form of digital attack which can send commercial

airliners off course, has entered an intriguing new dimension,

according to cybersecurity researchers: The ability to hack

time.

There has been a 400% surge in GPS spoofing incidents

affecting commercial airliners in recent months, according to

aviation advisory body OPSGROUP. Many of those incidents involve

illicit ground-based GPS systems, particularly around conflict

zones, that broadcast incorrect positions to the surrounding

airspace in a bid to confuse incoming drones or missiles.

"We think too much about GPS being a source of position, but

it's actually a source of time," Ken Munro, founder of Pen Test

Partners, a British cybersecurity firm, said during a

presentation at the DEF CON hacking convention in Las Vegas on

Saturday.

"We're starting to see reports of the clocks on board

airplanes during spoofing events start to do weird things."

In an interview with Reuters, Munro cited a recent incident

in which an aircraft operated by a major Western airline had its

onboard clocks suddenly sent forward by years, causing the plane

to lose access to its digitally-encrypted communication

systems.

The plane was grounded for weeks while engineers manually

reset its onboard systems, said Munro. He declined to identify

the airline or aircraft in question.

In April, Finnair temporarily paused flights to

the eastern Estonian city of Tartu due to GPS spoofing which

Tallin blamed on neighboring Russia.

GPS, short for Global Positioning System, has largely

replaced expensive ground devices that transmit radio beams to

guide planes towards landing. However, it is also fairly easy to

block or distort GPS signals using relatively cheap and easy to

obtain parts, and limited technological knowledge.

"Is it going to make a plane crash? No, it's not," Munro

told Reuters.

"What it does is it just creates a little confusion. And you

run the risk of starting what we call a cascade of events, where

something minor happens, something else minor happens, and then

something serious happens."