How can one be absolved from backbiting committed against unknown individuals or groups?

We have previously issued several fatwas concerning how a backbiter should repent from backbiting and seek absolution from those they have backbitten. Here, we add an exhortation for you to persevere in repenting from backbiting, to be diligent in it, and not to return to it. And whoever repents, Allah accepts their repentance.