The present invention provides a network security method, which comprises the steps of: maintaining information on blocked countries, to be blocked from data communication, in a blocked country database; identifying an external IP address by extracting at least one of a source IP address and a destination IP address of a communication packet transmitted on a network; identifying a country to which the identified external IP address belongs; and blocking the communication packet when the country to which the identified external IP address belongs is included in the blocked countries.