In Judaism, Satan, or more properly Ha-Satan, is still very much a very loyal and very obedient angel of God. He does not disobey god, he worships only god, and he is a very powerful agent of god. The idea of him rebelling against god and becoming the enemy of god did not come about until Christianity made him an enemy, perhaps to make Christianity more congruent with Pagan religions that typically had an evil counterpart to the slain and resurrected god. Islam apparently kept the idea of Satan being the enemy of God, but changed the reason of rebellion (according to Christianity, Satan rebelled because he wanted to be god).