Something is triggering "Directadmin Brute Force Manager" as that is what blocked your IP.
Among other things this would include bad logins to the server but it also monitors for instance wp-login.php activity if you have wordpress installed. Your server seem to be doing it a fair bit more often as of late though so it is possible there's something that needs tweaking, I'll have a word with another admin that was looking into this the other day as well and see what he found out.
I have removed the block for now.