Do any of your aircraft use GPS as a position input to the FMS (Flight Management Systems)?
If so, you're using GNSS.
As far as "spoofing" goes, I would tend to think that this is a wartime issue where incorrect GPS information can misdirect aircraft and missiles.
FMS systems uses several position inputs. VOR/DME and IRS being two of them. GPS inputs are not required.
"If" a GPS signal was also being used (and being spoofed), a position comparison warning would alert the crew that something was wrong with the GPS. It is able to be deselected. If not..... a breaker can be pulled.