If they are flying without ADS-B (which is legal for the military when needed) they won't be picked up by this system so no filtering needed.
https://www.aviationtoday.com/2019/07/23/new-rule-allows-mil...
Not just because of the potential safety issue, but because of how easy it is to track you.
In many areas, they have Wide Area Multilateration equipment installed that will show the real location of the transmitter, instead of the fake GPS coordinates you transmit. Normally it's there to double-check the ADS-B coordinates are correct, to track older planes without ADS-B, and to give true altitude readings, but it will track illegal transmitters as a side effect.
Even in areas where they haven't installed a permanent MLAT system, they usually have some sort of equipment that can track down a 1090MHz transponder. For-example, search and rescue planes often carry one.