Satan is called the Prince of the Power of the Air (Ephesians 2:2), the god of this world (2 Corinthians 4:4) and the prince of the world (John 12:31, 14:30). He is also identified in the Bible as the deceiver of the world (Revelation 12:9) and the spirit working in the unsaved (Ephesians 2:1). Satan is shown in Scripture to wield great power in this world and to have great influence in the world.
Satan is a mighty creature and a beautiful angel who rebelled against God. Satan’s first recorded interaction with humanity was to deceive mankind and lead them into sin. Since the fall of Adam and Eve, Satan has held sway over the hearts of men and has had great authority over the course of this world. Satan’s angelic followers, the demons, are able to take over the lives of people. Demons can possess people and cause them to harm themselves and others. (Mark 5:2-5; 9:17-22) Demons apparently exercise great authority over the governments of this world. (Daniel 10:13; Ephesians 6:12) At the end of this age Satan will control a powerful world leader who will wreak havoc on the world and persecute thousands of people. (Revelation 13:1-2)
Despite Satan’s great power, his power is not limitless. He is the god of the world, but he is not God. Satan is a creature always under the control of God. God limits Satan’s activities, and accomplishes His good purposes in all things despite Satan’s malice. The greatest example of this is Satan’s control of Judas Iscariot. The Gospel of John says that Satan filled Judas’ heart to betray Jesus. Judas’ betrayal was evil and according to the wicked will of Satan. Satan sought to hinder the plan of God, but Judas’ betrayal directly resulted in Jesus’ death on the cross. God allowed Satan to control Judas and He allowed Judas to reject Jesus so the greatest good in the world- the salvation of men- could be accomplished on the cross.
Why does God allow the Satan so much power and control? The Bible does not give a clear or simple answer. However, some of what the Bible teaches about God’s allowing evil also answers why God allows Satan such power. God allows Satan to work so His name will be glorified. Just like God used Pharaoh’s hard heart to bring Himself glory (Exodus 14:4), so God is using Satan to glorify His name. God also allows Satan power to show the world the terribleness of sin. If men experience the pain of sin in this life and repent of their sin, they will be saved from eternal destruction (1 Corinthians 5:5) God also allows Satan power to test Christians to make them more like Christ. God used Satan’s affliction of Job to reveal to Job his own pride and wrong view of God, and God is doing the same in Christian’s lives today.
Though a complete answer cannot be given to this question everyone can be certain of three things. First, God permits Satan to trouble this world as part of the righteous punishment of sin. Sin always brings forth death and God uses Satan as one instrument of accomplishing this judgment. Second, God is allowing Satan the temporary power to afflict the world to bring about a far greater, eternal good. (Genesis 50:20) Part of this good is the salvation of mankind (Acts 17:26-27) Last, God allows Satan the power to trouble men to shape Christians into Christlikeness and bring eternal good to them. (Romans 8:28-29)