Is it considered backbiting for someone to speak ill of another person, mentioning their name, in front of me, even if I don't know that person? And will I be held accountable for listening to such talk? And is it a condition that both parties know the person being referred to for it to be considered backbiting?

Among the conditions for backbiting to be unlawful is that it must be about a known person. If the person is unknown to the listener, it is not considered unlawful backbiting unless it is easy to identify them. An-Nawawi mentioned in his commentary on Muslim, citing Al-Mazari, that unlawful backbiting is the mention of specific individuals or groups by name, and that speaking about unknown women was not backbiting. Qadi Iyad supported this, emphasizing that if a person is unknown to the listener, their essence is not harmed unless they are identified. Ibrahim said: "It is not backbiting unless its subject is named, or indicated in a way that makes them understood."