TL;DR my first vps got hacked, the attacker flooded my server log when I successfully discovered and removed him so I couldn't use my server anymore because the log was taking up all the space on the server.

The first Linux VPN I ever had (when I was a noob and had just started with vServers and Linux in general, obviously) got hacked within 2 moths since I got it.
As I didn't knew much about securing a Linux server, I made all these "rookie" mistakes: having ssh on port 22, allowing root access via ssh, no key auth...

So, the server got hacked without me even noticing. Some time later, I received a mail from my hoster who said "hello, someone (probably you) is running portscans from your server" of which I had no idea... So I looked in the logs, and BAM, "successful root login" from an IP address which wasn't me.

After I found out the server got hacked, I reinstalled the whole server, changed the port and activated key auth and installed fail2ban.
Some days later, when I finally configured everything the way I wanted, I observed I couldn't do anything with that server anymore. Found out there was absolutely no space on the server. Made a scan to find files to delete and found a logfile. The ssh logfile. I took up a freaking 95 GB of space (of a total of 100gb on the server). Turned out the guy who broke into my server got upset I discovered him and bruteforced the shit out of my server flooding the logs with failed login attempts...

I guess I learnt how to properly secure a server from this attack 💪