The most recent Unsafe Airspace Summary from the Flight Services Bureau cautions pilots about chronic GPS disruptions in Egypt, Turkey, North and South Korea, and the Philippines. A subsequent update identified problems in Cypress as well.
The US Maritime Administration recently updated its notice about GPS disruption in the eastern Mediterranean with an Alert about specific problems at Port Said, Egypt.
GPS jamming by Russian forces in Syria, the Ukraine, Moscow, the Baltic Sea and the Black Sea, and by China in the South China Sea have also been in the press recently.
Disruption events have also been reported by aviation interests in France, Mexico, and at numerous locations across the United States.
The low cost of GPS jammers and the ease with which they can be obtained (we have identified 15 different on-line stores) means that there are few places on the planet that are not threatened.
‘A prudent navigator uses all means available to determine position’ – Bowditch (emphasis added)