The names are Mizaru (covering eyes and sees no evil), Kikazaru (covering his ears and hears no evil), Iwazaru (covering mouth and speaks no evil). But they have a fourth friend, the image of which is much rarer.
She embodies the principle of "do not commit evil" and covers the arms and stomach area of the perineum. Since the Japanese consider the number 4 unlucky, the fourth monkey is mentioned very rarely.