The job of a welfare fraud investigator is to do what is sounds like, which is to investigate welfare recipients who are suspected of fraud. This duty protects the federal government as well as the tax payers, whose taxes fund welfare programs. There are many different ways that people commit welfare fraud. The most common method is a person collecting a welfare check when they are already receiving enough money from other sources rendering them ineligible for welfare. This may be difficult to detect as some people make money by working under the table and not reporting their income or filing taxes.