Change DNS server
change DNS server to use OpenDNS
Settings > Network > Select network connection to edit
IPv4 tab, add DNS servers 208.67.222.222 and 208.67.220.220
IPv6 tab, add DNS servers 2620:0:ccc::2 and 2620:0:ccd::2
If you look at /etc/resolv.conf, you should only see the DNS addresses you added.
cat /etc/resolv.conf
For example,
nameserver 208.67.222.222
nameserver 208.67.220.220
Check if you are using OpenDNS at https://welcome.opendns.com/.