I've often wondered if a WW1 stringbag could fly right past modern air defenses without being detected or tracked.
(Similarly, during the Battle of Britain the Hawker Hurricane was notable for the way German 20mm cannon shells passed through its doped cloth-on-tube airframe. No impact to trigger the fuzes.)
Another interesting property of the An-2 is the incredibly high cross-section of the aircraft means slow flight speeds and very high lift, the aircraft really doesn't have a stall speed due to spring-deployed slats that snap out as airspeed drops... but whatever you want to call the stall speed it's lower than 30 kts. So in a stiff headwind you can fly the aircraft onto the ground in full control at zero ground velocity, or actually while being pushed backwards by the wind.
Wouldn't be enough to deter a dedicated attacker at short range especially with a sufficiently high radar frequency (the engine and other metal parts become a bigger multiple of the wavelength), but would you be able to pick it up at 50-100 miles with longband search radar? especially at low altitude? Probably not. Especially random ex-Soviet crap like a lot of countries have.
Don't knock primitive tech, sometimes it works. The An-2 is archaic but it's a very competent bushplane/light cargo aircraft for squad-level paratroop or liason operations. And it's well-adapted for rustic operations like Russian/Canadian bush, or Korea.
https://en.wikipedia.org/wiki/Antonov_An-2
https://www.youtube.com/watch?v=A3tpV9vUTPo
http://www.smithsonianmag.com/smart-news/why-north-korea-usi...