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 51.103.75.40 on port 53011 TCP:
$ telnet 51.103.75.40 53011
Trying 51.103.75.40…
Connected to 51.103.75.40.
Escape character is ‘^]’
Referencing malware samples:
MD5 aa2957c1912b583d18c3fad0a1dbe455