What's the problem if you have a secure password? It's probably more likely that the datacenter or house where your server is located will flood or catch on fire before a bot guesses your user and secure password.
They're just trolling for suckers with dictionary passwords. Or am I missing something?
If your log files fill up with this kind of scripted probe chaff, you'll never see the one line in that log file that you *should* pay attention to.
This is oversimplification, but allowing log files to be flooded with this kind of stuff makes life more difficult.