Cyber-attacks in Japan in 2016 reached a record of about 128.1 billion, or a 2.4-fold increase from the previous year, the National Institute of Information and Communications Technology announced.
Attacks originating from China accounted for the largest portion by country.
According to the Internal Affairs and Communications Ministry, cyber-attacks targeting so-called internet of things (IoT) related devices, such as webcams and routers for home use, made up about half of the total - a sharp increase from 26 per cent in 2015.
The attacks appear to be using IoT appliances as a stepping-stone for eventually infecting computers at government organisations and corporations.
IoT appliances are said to have less protection against viruses compared to personal computers and smartphones, thereby making them easy targets.
Home appliances such as TV sets are increasingly adopting IoT innovations, and the ministry plans to draw up measures to protect them.
The NICT has been monitoring cyber-attacks by installing sensors on domestic networks.
The number of cyber-attacks has increased year on year since 2005, when the state-run research and development institute began monitoring them.
Recently, the figures have almost doubled year-on-year.