Unfortunately this most likely indicates that your droplet has been compromised and malware is running on it either to attack other servers or with the CPU use here, possibly mining cryptocurrency.

You should immediately back up any needed files and create a new clean server to migrate to. Cleaning an infected server can be an extremely time consuming and often futile process. Once you have a new server set up there are a few steps you can take to help secure it:

• Use an SSH key for authentication rather than a password

• Configure automatic security updates

• Change the default SSH port

• Enable the local firewall.

These guides will help you with these steps:

Unattended updates
Initial Server Setup (includes ssh keys, firewall, changing ssh port)