TL;DR - Check the DNS settings on your DrayTek router and install new firmware.
In May 2018, we became aware of new attacks against web-enabled devices, which includes DrayTek routers. The recent attacks have attempted to change DNS settings of routers. We are in the process of releasing updated firmware which you should upgrade to as soon as it is available but also immediately follow the advice below:
Update your firmware immediately, or as soon as updated software is available. Before doing the upgrade, take a backup of your current config in case you need to restore it later.