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 51.105.25.115 on port 6522 TCP:
$ telnet 51.105.25.115 6522
Trying 51.105.25.115…
Connected to 51.105.25.115.
Escape character is ‘^]’
$ dig +short njratfdf.freedynamicdns.org
51.105.25.115
Referencing malware samples (MD5 hash):
4b169eac01ae414ca663e2f334d97cc3 — AV detection: 58 / 71 (81.69%)