The Russians may not be jamming GPS (this is a VERY hard thing to do, the signal is coming from above and the receive antenna is generally designed to be hemispheric — meaning excludes signals not from upwards).
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GPS can be jammed. The signal is baseband spread spectrum so power requirements are reduced and multiple signals can be sent using the same frequency. Jamming is simply putting out enough power to mask the low-power GPS signals. Russians have been doing it for over 20 years.
Spoofing (false signals) the GPS is a little tougher but also being done within the last ten years or so if memory serves. That drives the navigation off so the target is missed. I’m not going to chase it.
You might try looking up navigation errors using GPS reported by aircraft pilots in the middle east regions. That’s the spoofing problem.
GPS is very easy to jam. I’m an airline pilot and I see it quite a bit.