At the beginning of His ministry, Jesus was tempted by the devil. Two of the three temptations began with a barb of doubt: "If thou be the Son of God" (verses 4, 7, 10).
The Savior also taught His followers through scriptural examples how to overcome evil. Teaching people to resist evil or face dire consequences, the Master Teacher cited an Old Testament account: "It shall be more tolerable for the land of Sodom and Gomorrha in the day of judgment, than for that city [those who rejected His gospel]" (Matthew 10:15).
If we obey it, the word of God has an inherent protective power: "Whoso would hearken unto the word of God, and would hold fast unto it, they would never perish; neither could the temptations and the fiery darts of the adversary overpower them" (1 Nephi 15:24).
One of my favorite scriptures to resist Satan today is this verse: "Mine eyes are upon you. I am in your midst" (D&C 38:7). It dispels forever the lie "no one will know."