How can I get no damage when glitching?

I always see people lag jumping the wall at B then jumping on top of the roof of the hotel and sniping. I do this but my HP goes down. Are they using hack or what?


Eagle Eye if you didn't know.

There is a no bug damage hack, or also called no glitch damage
They use that and in some spots u wont lose ur HP like in mutant mode port the crate spot