housing benefit fraud

Housing Benefit Overpayment

The person renting my house has been cought for fraudelently claiming housing benefit and my rent payment has been frozen. Looking into this it appears that the benefit department can claim the money back off me as it was paid directly to me, although at this time the benefit people have not been in touch I would like to know my position in this situation, would it be better to tell the benefits that i was aware sombody was in my property and that i thought this was taken into account by the benefit department or deny I had any knowledge of this fraud. To be honest I had realised somebody had moved in and it constituted a Housing Benefit fraud but unwisely turned a blind eye. Do you think this will prove costly