Should I and how do I file a fraud claim against my overtenent for not paying my rent to the landlord?

I have been subletting my apartment from an individual for over a year. As it turns out, for the last five months he has not been paying the landlord the rent I have been giving to him (he also has my security). It amounts to nearly $8000. Should I file a civil claim against him? A fraud claim? Both? The landlord’s attorney is threatening to come after me for the back rent. I would like to get as much of the rent from him and pass it on to the landlord, it would make me feel a lot better about the situation. Any advice would be appreciated. Thanks.