Replace "who(m)" with a pronoun. Which one sounds better?
. . .who/they attack everything around them.
. . .whom/them attack everything around them.
Note, the verb is "attack", its object is "everything" and its subject is "who". Use "whom" or "what" for the verb's object:
They attack everything. => What do they attack?
They attack us. => Whom do they attack?
Grammar Help: I think that whom should be changed to who.