Tokyo Metropolitan Police Department: Home routers being abused as sources of cyberattacks. Home routers are difficult to investigate because they only keep a record of connections for a short period of time.
It is highly likely that overseas criminal groups used it as a "stepping stone" for the attack. How to protect your home router from cyberattacks: Protect your router from such damage by changing the settings on your router to prevent it from being used for cyberattacks, or by using a VPN function to hide your connection.