Looks like an Olive snail to me, but I am not expert on snails. That is the common name for a whole family of snails which include a lot of different species. My understanding was they were not beneficial to a tank.
Years ago Dr. Ron Shimek had a section of the MarineDepot.com forum and if he didn't know a close ID he knew someone who could give a pretty well educated guess. I wouldn't be sure who to point you to for a great ID though.
I personally would ask around more, but if I was able to I would pull it out of the tank into an isolated container.(perhaps a plastic sealed jar floating in your sump, so the temperature and salinity stays the same)