Guarding Your Ears
Answer: The basic prohibition mentioned in halacha is against “accepting” lashon hara. That means one is not allowed to believe that what has been said is true. It is difficult, however, to disbelieve something you hear from a friend. It is therefore advisable to nip the problem in the bud by asking your friend to change the subject the moment he begins to speak about someone else, even if this makes you appear like some tzaddik. Should your friend insist on continuing with his slanderous report, it is your duty to inform him that you cannot accept that the object of his lashon hara did something improper.
Guarding your tongue is an important responsibility but so too is guarding your ears.