DirectAdmin since version 1.39 has function to detect brute force attack (Info) but DirectAdmin didn't block IP that brute force us. It just warn and annoy us by sending an email. DirectAdmin already provide how to automatic block IP when detect brute force for CentOS/Fedora here but they didn't provide for Debian so I will do for you

From How to choosing PHP module for Apache so I decided to use mod_fcgid on my DirectAdmin private hosting. This is how to

• Install DirectAdmin on your server. I suggest to use this how to on fresh DirectAdmin without any users. But if you want to install on DirectAdmin that have users, you must create and setting file and folder for users manually.
• I used Debian 6 64-bit but I think you can adapt my how to to install on CentOS and Redhat
• Run these command