Ask HN: Recruiters sending candidates that already reached out to me

I've been receiving emails from recruiters offering candidates for a job I posted on the whoishiring from many months ago. I already received his resume from a direct communication with the person. I am concerned that, if I do decide to go ahead with the candidate, the recruiting firm will try to claim that by din of having his resume I would owe the recruiter a finding fee. Is this something I should be concerned about? Is there anyway I can protect myself from this type of attack in the future?