To be clear, there is no such thing as a aircraft-specific transponder. Transponders emit a code as assigned by ATC.
We are “running” the airspace over there and we track the region’s traffic. There is no way Israel would be able to pull tis off unless they coordinate with us.
No matter, anyway, Israel won’t do it. They haven’t the weapon to attack the sites. We. . .on the other hand. . .
I am quite familiar with radar. The higher the frequency, the better the resolution and the harder it is to fool it by flying in close formation.