Hi Henry,
Here's some steps that might help you with that concern.
1. Run Malwarebytes. https
/www.malwarebytes.org/mwb-download/
2. Once done running scan with Malwarebytes run Adwcleaner. http
/www.bleepingcomputer.com/download/adwcleaner/dl/125/
for more detailed instruction please refer to this link.
http
/malwaretips.com/blogs/ads-by-dns-unlocker-removal/
Thanks