Here's a recent tidbit from Patrick Madrid's blog: Warning signs of a diabolical spirit and how to recognize them. Some of the list makes sense, here though are two to ponder:
14. Lack of deep devotion to Jesus and Mary.
15. Scrupulous adherence to the letter of the law and fanatical zeal in promoting a cause. This characteristic readily opens the door to diabolical influence in reformers and demagogues.
OK, let's see, I'm not really devoted to Mary, and I enjoy the writings of certain reformers.... But then again, this isn't an official infallible list, but rather "the teaching on this subject by the late Dominican theologian, Fr. Jordan Aumann, O.P." Never mind.