CSF

Block IPs with Brute Force Monitor in DirectAdmin using CSF

Source: https://help.poralix.com/articles/how-to-block-ips-with-csf-directadmin-bfm

Regular install of CSF

cd /usr/local/src
wget http://www.configserver.com/free/csf.tgz
tar -xzf csf.tgz
cd csf
./install.directadmin.sh

Now login as Admin into directadmin or WHM, and click the link ConfigServer Security & Firewall

You'll probably want to add your WAN IP here--you can find out what it is here: http://www.ip-secrets.com/

Then add your WAN IP into Quick Allow column.