My understanding is that fraud is a definition of a criminal behavior/method/act. A person can -commit- fraud, but if they use fraud against someone, they are 'defrauding' someone.
You don't 'fraud' someone, you 'defraud' them.
However, if people in the field commonly use the term "fraudster" it is easier on the tongue than the standard noun construction "defrauder" (my opinion would be to go with the other answer lol)
merriam-webster's definition of defraud
Definition of defraud
: to deprive of something by deception or fraud
defrauder \di-ˈfrȯ-dər\ noun