Recently, some countries deploy global cyberattacks that not only impose destructive measures to the system of industries or infrastructures but also as information warfare, including social networking service (SNS) and other media that affects election results or democratic processes, which becomes a threat to democracy. Thus, this operation is recognized as “disinformation.” This paper demonstrates cases of disinformation in cyberspace, and focuses on legal problems in the international law and countermeasures of legal systems in each country.Consequently, it is found to be challenging to deal with disinformation on the national scale. As there is a limit regarding the regulations by international law, at the present, it is essential to provide the national law about it. I classified the types of countermeasures to find better countermeasures to it based on my considerations, as the number of disinformation cases increased. The regulation for disinformation could violate the freedom of expression and democracy. Therefore, posteriori sanctions against foreign state actors should be applied, and regulations on the contents of media and platformers need to be practiced carefully.