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 52.188.147.221 on port 5621 TCP:
$ telnet 52.188.147.221 5621
Trying 52.188.147.221…
Connected to 52.188.147.221.
Escape character is ‘^]’
Referencing malware samples:
MD5 906fc789e43caebcaecff3a0c7e54b30
MD5 e3cb5fb484ec5e048872f59a9d48bcd3