1. A method comprising: employing a computer system to determine an aggregate fraud score of a target document as a combination of a first fraud score and a second fraud score of the target document, wherein the first and second fraud scores are determined according to distinct fraud-evaluation procedures; employing the computer system to determine a third fraud score of the target document; in response to determining the third fraud score, employing the computer system to modify the aggregate fraud score by a first amount determined according to a product of the third fraud score and a difference between the aggregate score and a maximum allowable aggregate score; and in response to modifying the aggregate fraud score, employing the computer system to determine whether the target document is fraudulent according to the modified aggregate score.