Creepy Crab ID Please

[LeanneP]

It amazes me that I have had my tank for a year and a half and I suddenly see this furry brown and black crab in my rocks that I have never seen before. I can't get a photo of him because he just looks like the rocks. He is brown with black claws and kind of fuzzy. I have done some searches but can't find any that look like that. Anyone know what it is? Is he good or bad?

Leanne