A vulnerability countermeasure device stores configuration information associating multiple computers connected via a network and software possessed by each computer, vulnerability information associating the software with information related to the vulnerability of the software, and countermeasure policy information associating the software with a countermeasure policy to be executed if there is a vulnerability in the software; calculates the computer that data will reach based on information related to a route of the data included in the data received from a used terminal; acquires software existing in the computer based on the calculated computer and configuration information; assesses whether or not there is a vulnerability in the acquired software based on the acquired software and the vulnerability information; and is provided with countermeasure unit for executing a countermeasure to a vulnerability in accordance with a countermeasure policy with respect to the software assessed to have the vulnerability.