There have always been false prophets in the world.  The most dangerous ones are those who attempt to come in among us secretly. 

2 Peter 2:1-2 (ESV)
But false prophets also arose among the people, just as there will be false teachers among you, who will secretly bring in destructive heresies, even denying the Master who bought them, bringing upon themselves swift destruction. ² And many will follow their sensuality, and because of them the way of truth will be blasphemed.

Jesus also referred to these, calling them ravenous wolves.

Matthew 7:15 (ESV)
¹⁵ “Beware of false prophets, who come to you in sheep’s clothing but inwardly are ravenous wolves.
Do you see how Jesus began this warning?  “Beware,” He said.  This should immediately put us on alert.  We should also notice how these wolves appear.  They are always in disguise, that is, dressed like sheep.  They look innocent enough, but they have sinister motives.  Because of the presence of these false teachers, Paul warned the elders of the church at Ephesus to stay alert.

Acts 20:28-31 (ESV)
²⁸ Pay careful attention to yourselves and to all the flock, in which the Holy Spirit has made you overseers, to care for the church of God, which he obtained with his own blood. ²⁹ I know that after my departure fierce wolves will come in among you, not sparing the flock; ³⁰ and from among your own selves will arise men speaking twisted things, to draw away the disciples after them. ³¹ Therefore be alert, remembering that for three years I did not cease night or day to admonish every one with tears.

This was not Paul being paranoid.  He was not guessing about wolves coming in to devour the flock.  He said, “I know…”  For three years he never stopped warning and admonishing them to be alert.  Some of these wolves would come from without, and some from within, but they would come.  Their goal would be to draw away disciples, which is always the goal of the false teacher or prophet.  And remember, they are always in disguise.

2 Corinthians 11:13-15 (ESV)
¹³ For such men are false apostles, deceitful workmen, disguising themselves as apostles of Christ. ¹⁴ And no wonder, for even Satan disguises himself as an angel of light. ¹⁵ So it is no surprise if his servants, also, disguise themselves as servants of righteousness. Their end will correspond to their deeds.

How do we recognize these false prophets?  Jesus said we will know them by their fruit (Matthew 7:16).  It may be the fruit of their character.  Peter referred to them as those who were guilty of sensuality.

Immoral living, however, is not the only way to determine that one is a false teacher.  Peter also mentioned their destructive heresies, which would include, not only what he was dealing with specifically, that is, a denial of Christ, but any doctrine that is destructive to the soul.  When someone teaches the commandments of men instead of the Word of God, that person is a false teacher.  Beware of anyone who cannot prove his or her teaching by the Bible.  Make sure, as I often say, that teachers of God’s Word can put their finger on the passage.

As you wind down for the night, think about these things.