Recently, I have been reading a lot of my ubuntu log files (in /var/log/auth.log), and I can see that some IP addresses are actually trying to 'brute-force' their ways into my VM using SSH by testing a lot of very simple combinations (like root usernames, or very common apps usernames such as php or mysql).
Just curious, how do these attackers find about my particular IP? Are they performing this attack on a lot of different machines at the same time or is it just me?