Answer
One has to shave the scrotum and the hair around it as well.
By hind parts is meant the circle around the anus, as it is very likely that faeces could get attached to any hair present there. (Raddul Muhtaar Vol.2 Pg.481-H.M.Saeed, Tahtaawi alal Maraaqi Pg.527-Ilmiyyah, Fathul Bari Vol.10 Pg.343)
and Allah Ta’ala Knows Best
Mufti Ebrahim Desai