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 5.188.42.121 on port 443 TCP:
$ telnet 5.188.42.121 443
Trying 5.188.42.121…
Connected to 5.188.42.121.
Escape character is ‘^]’
doemek01.top. 600 IN A 5.188.42.121
bojofa05.top. 600 IN A 5.188.42.121
bojozb04.top. 600 IN A 5.188.42.121
bojshi03.top. 600 IN A 5.188.42.121