I have written before about scans for DNS over HTTP(s) (DoH) servers. DoH is now widely supported in different browsers and recursive resolvers. It has been an important piece in the puzzle to evade various censorship regimes, in particular, the “Big Chinese Firewall”. Malware has at times used DoH, but often uses its own HTTP(s) based resolvers that do not necessarily comply with the official DoH standard.
Article Link: https://isc.sans.edu/diary/rss/29488