The Bible makes clear that the tactics of the devil fall into two major divisions. He attacks the human race both directly and indirectly. He is capable of a direct confrontation with human beings, and an indirect approach.
And through these two avenues he maintains his worldwide control over the race of men. The Bible indicates that there are fallen hosts of angels called demons, whom Paul calls here "the principalities and powers, the world rulers of this present darkness, the spiritual hosts of wickedness in heavenly places."
A direct attack of the devil upon a human life is an obvious thing, but this is something devious, something circuitous, difficult to detect. This indirect approach comes largely through two media, or channels. One is what the Bible calls "the world," and the other, "the flesh."