drones are invisible to radar.......or clearly russia(or ukrain) would not be dealing with strikes far from the front lines also, hypersonic missles are now a thing, and the hit faster than any radar or interceptor can register but yes if you were worried about Portugal trying a sneak attack, then clearly they would use the wind turbine shielding attack vector from weaponised shipping cans placed on container ships

They are not (necessarily) invisible, that depends on size & many other variables.

Also, hypersonic missiles are perfectly vusible on radar.

Drones are regularly intercepted in the Ukraine war. Patriot batteries have intercepted kinzhals.