in Job, Satan encourages or talks God into allowing him to inflict calamities on the man, ..and God agrees.
christians see Satan more as an autonomous force opposed to God , rather than an agent subordinate to Gods will.
Unlike rabbinic jews , kabbalistic Jews like christians really go for the Satan thing and offer a rich and detailed portal of evil, demons ,spirits, etc.
Satan is the symbolic personification of mans resistance or barrier in submitting to divine will.
-Bulletproof and Waterproof don't mean Idiotproof.