This often happens when you use a pre configured copy/paste settings to mine cryptos on ubuntu, you will need to look into the codes but the best thing to do is to personally write the codes from the scratch and do not copy paste into the droplet like safe screen stuffs.
Yeah. Droplet was also totally fucked up. And lack of security even after password changing and mailing digital ocean.
That's a pretty big company and they should have a decent security set up for you to use. The only draw back is that mining may be against their terms, so be quiet about that.