Impostor & Imposture

Impostor is a pretender or someone who engages in deception under an assumed name or identity: “The police officer got his assistant arrested as he was acting as an impostor trying to pass on the secrets of the office to the press .”
Imposture , on the other hand, means deception by fraudulent impersonation or an instance of deception under an assumed name or identity: “The man who pretended to be the ticket examiner and charged the passengers was arrested for his imposture.”