The due diligence starts with the contracting agency before forwarding the paperwork to the prospective airline of employment.
They should confirmation of employment from previous companies flown for. However a major problem is that many airlines that pilots claim to have worked for may have gone bust, thus no way to validate records. There may be an isolated instance where a manager of a bygone carrier has records stored on a computer some place. That however is a long shot.
The agency should obtain a PRIA records report from the pilots' country aviation agency to ensure the validity of the airman's certificate, and history of violations if any.
If hired and found to be a fraud, then the airline needs to notify their respective DGCA. Then the airlines' DGCA should be proactive in notifying the pilots' DGCA as validations are conditioned on a valid airman certificate from their native country.