MAC DNS poisoning

hi,

just noticed that my DNS server address values in my Macbook are 85.255.116.90
85.255.112.128. I searched it over google and i found out that it is indeed malicious. i tried to remove it however, it is grayed out and I cannot remove it from the list. i also tried to flush the dnscache. however, it is still the same. do you have any suggestion?