There is a war between Sunnis and Shiites, the first have Saudi Arabia like the "leader" and the Shiites has Iran like leader......ISIS are a Sunni extremist organization, for that reason i sayed what i sayed, the Sirias war and the conflict with ISIS are all part of the same thing: Saudi Arabia, ISIS and the most part of the Sunnis countrys in one side, Iran, Siria, Hezbolla, the Shiites groups of Irak and Yemen in another side.
For this reason ISIS wont atack any "sunni" target?, of course they do, in fact some sunni monarchys pay to ISIS to dont make nothing to them.