Ephesians 6:12 (NIV) For our struggle is not against flesh and blood, but against the rulers, against the authorities, against the powers of this dark world and against the spiritual forces of evil in the heavenly realms.
Paul tells us that we need to be aware of Satan's schemes so that he cannot outwit us.
(2 Corinthians 2:11 NIV) in order that Satan might not outwit us. For we are not unaware of his schemes.
Learn more about Spiritual warfare from this series.