What are the red exclamation marks on bandit camps?

I'm sure this info is out there somewhere but I've tried searching for it and have had no luck. Most of the bandit camps I have left have a red exclamation mark on them, but a few of them do not and I'd like to know why. It doesn't appear to be based on difficulty since I have medium ones with the exclamation mark but then there's some marked hard that don't have it. My theory is that it has something to do with the total health of the mobs since the ones without it tend to mostly have dogs and rangers and few high health melee.

I've always been told that those camps have special difficulty. Either some first strike troops, or something that bypasses your melee folks and goes right for the juicy, tender Cavalry behind them. Definitely something you want to run through the simulator first. I don't think it's anything quantifiable like total health, since I've even seen (Easy) camps that have it.

Borkin

The Red Exclamation Marks means that they are a Difficult Camp and So should probably use the Combat Simulator to see the best way to kill them. If the Camp has a Skull it means it will require multipule waves to kill it.

Atleast I think, I can't remember.

from what i understood when they were 1st inserted into the adventures, the red '!' above a camp is supposed to signify that it is a leader camp. RGC is correct with the skull meaning it is a more difficult camp, though the dark castle on the dark priests adventure has the skull, and i clear it w 1 wave using a vet

I think the skull means that there is a boss. Exclamation mark means that it is suppossed to be difficult (although sometimes there are ways to make it not so hard).