Is it permissible to inform people of what a backbiting man says about them, a man who fabricates lies to show their depravity and to exonerate himself, or is this considered backbiting?

Backbiting (namimah) is among the major sins and is not permissible except to prevent harm to others if that harm cannot be averted otherwise, in which case it becomes advice. However, informing relatives of what this person said about them is backbiting (namimah) and is not permissible. Instead, one can warn against him and expose his true nature by stating that he is a liar, and this is not considered forbidden ghībah (slander/backbiting).