Some people may already know about one kind of GPS spoofing. Android phone applications will spoof a phone's GPS position, at the Google store. It doesn't transmit a GPS signal; it just fools the phone's GPS, running the application.
I assume this is for general mischief like bypassing geo-locking, a fraudulent company driver, or an adulter trying to hide their position.
The following is related to actually transmitting bogus GPS signals.
"Ships fooled in GPS spoofing attack suggest Russian cyberweapon"
By David Hambling
Reports of satellite navigation problems in the Black Sea suggest that Russia may be testing a new system for spoofing GPS, New Scientist has learned. This could be the first hint of a new form of electronic warfare available to everyone from rogue nation states to petty criminals.
On 22 June, the US Maritime Administration filed a seemingly bland incident report. The master of a ship off the Russian port of Novorossiysk had discovered his GPS put him in the wrong spot – more than 32 kilometres inland, at Gelendzhik Airport.
After checking the navigation equipment was working properly, the captain contacted other nearby ships. Their AIS traces – signals from the automatic identification system used to track vessels – placed them all at the same airport. At least 20 ships were affected.
While the incident is not yet confirmed, experts think this is the first documented use of GPS misdirection – a spoofing attack that has long been warned of but never been seen in the wild.
This is obviously a real hazard for transport. Satellite navigation have to be used to determine location. These system are the US's GPS, Russia's GLONASS, EU's Galileo, China's BeiDou-2.
As people may know, satellite navigation basically use flying clocks.
Some infrastructure uses GPS to determine time. The common examples are the electric power grid, and the stock exchange.
The reason is GPS is stable, not jittery, and accurate to the nanosecond.
Internet based "Network Time Protocol", NTP, is really only accurate to the second. So NTP is OK for most application, but not stock trading, for example. Windows and Linux all have free built-in NTP clients, and don't require any additional hardware: the satnav receiver and antenna.
In theory misuse could target stock exchanges, as they also use GPS signals to set their internal clocks.
A hacker could set up a series GPS spoofers near a stock exchange, and slowly move to time forward. Then submit retro-active trades.
There are two way to defeat this attacks
1) use more than one satellite navigation system, GPS and either GLONASS, Galileo or BeiDou-2.
2) create two NTP servers, using GPS. The two servers would be used by all your internal systems. They should be in secret locations, away from all database and application servers.
Again NTP over-the-internet is jittery, and only accurate to the second. NTP internal servers are also a little jittery, so should be OK.