1. A malicious-module identification device for identifying and deactivating a malicious module operating on an information processing device connected to the malicious-module identification device via a network, the malicious-module identification device comprising: a hardware processor configured to operate as: a reception unit that receives results of tampering detection from a plurality of modules performing tampering detection; a determination unit that assumes that a module among the plurality of modules is a normal module, to determine, based on the assumption, whether a contradiction is detected in the received results of tampering detection, and to identify the module assumed to be a normal module as a malicious module when determining that a contradiction is detected; and a deactivation unit that outputs an instruction to deactivate the module identified as the malicious module, wherein the determination unit includes: an assumed normal module group storage unit that stores an identifier of the module assumed to be a normal module; an assumption unit that selects a module among the plurality of modules, assumes that the module is a normal module, and stores an identifier of the module in the assumed normal module group storage unit; an assumed normal module group generation unit that repeats, starting from the module assumed to be a normal module by the assumption unit, a process of assuming that a module in which tampering is not detected is a normal module and storing the corresponding identifier in the assumed normal module group storage unit; a contradiction detection unit that determines whether a contradiction is detected in results of tampering detection by modules corresponding to the identifiers stored in the assumed normal module group storage unit; and an identification unit that identifies, when the contradiction detection unit determines that a contradiction is detected, the module assumed by the assumption unit to be a normal module as a malicious module.