Ellen G. White wrote:The world is full of men and women whom Satan uses as his agencies. Christ has bought them with a price, —even His life-blood. But they have given themselves into Satan's control. They are blind, and have forgotten that they were purged from their sins. PH058 2.3
There are agents of Satan working both outside and inside the Seventh-day Adventist Church. Here is Ellen G. White's profile of the enemy on both sides:
A Profile of Satan's Agents