+1 on vermitted snails.
They usually have the spiral at base and can see a mucus web coming out the tube which they collect food and reel in
Few other common hitchhikers you may encounter
One of the greatest things about starting a reef tank is getting your live rock in and admiring all the diversity within it. The rock comes to life different creatures. This is a guide that I, along with a very well known critter identifier @KJ , have put together for the new reefer on what...
As others have said its a vermeil snail. They're super common and yes, occasionally cast what looks like spider's silk but they're not in the class of "burn with fire". Try to break it off at the base as they will multiply (very slowly in my experience).