Make sure your router doesn't allow admin access from the outside. Make sure you have a decent admin password. Disable any built-in cloud/ftp/sharing services

Make sure your router doesn't allow admin access from the outside. Make sure you have a decent admin password. Disable any built-in cloud/ftp/sharing services that you don't use or need. If you use them, make sure to use good passwords and remove any built-in/default account. Disable UPnP in the router if you don't really need it (and understand the risks).