Is the fox among the "Fawasiq" (noxious animals whose killing is permissible)? If not, what is the definition of a "mad dog"?

The fox is not among the 'Fawasiq' (mischievous or harmful creatures), and it is permissible to acquire, raise, and eat it. The 'Fawasiq' are those creatures whose killing, both within and outside the sacred precincts (Haram), was commanded in the Hadith. These are: the crow, the kite, the scorpion, the mouse, and the rabid dog.