The host at this IP address is obviously operated by cybercriminals. It is running a malware botnet controller which is being used to control infected computers (bots) around the globe using a trojan horse.
Malware botnet controller located at 185.251.91.198 on port 443:
$ telnet 185.251.91.198 443
Trying 185.251.91.198…
Connected to 185.251.91.198.
Escape character is ‘^]’
Malicious domains observed at this IP address:
cloudfsnbg.cc. 600 IN A 185.251.91.198
snatch.kim. 600 IN A 185.251.91.198
snatch.press. 600 IN A 185.251.91.198
snath.top. 600 IN A 185.251.91.198