Malwarebytes forum user posted a query regarding unknown malware that infected his friend’s computer that silently changed DNS settings on infected Mac computers. Ex-NSA hacker Patrick Wardle analysed the malware and found that it is indeed a ‘MaMi’ OSX/MaMi, which appears to be in its initial stage. The motive, author(s) behind the malware, and how it is spreading are currently unknown. None of 59 popular antivirus software is detecting this malware at this moment, so you are advised to use a 3rd-party tool such as a firewall.
Source: https://thehackernews.com/2018/01/macos-dns-hijacker.html