DirectAdmin doesn't come with a user-based block system. So if someone's messing with your site or doing something you don't want and you're merely a user and not an administrator, you can't just go in and add their IP to a block list and ban them from your site. The only real way I've found to be able to block based on IP without affecting the whole server is to use .htaccess files. I've spent many hours on this and did extensive testing to make sure everything works good, so it shouldn't have any problems. I tried making it so administrators could have a list of ALL the domains and apply/remove/view blocks in them, but the permissions on the home directory don't allow you to do a recursive read on all the directories inside it and DirectAdmin doesn't put a list of accounts in any environmental variables, so it's pretty much a lost cause from what I see.
Just wondering what you guys thought of it. It's free for whatever use you want. I know there's poor people out there like me who don't like paying $30 for simple software, so I'd rather not charge. :P Whenever it's installed (use the Plugin Manager), a new link will appear in the users' main page at the bottom labelled "IP Blocker". All they have to do is click that and everything's pretty self-explanatory (except the fact that you have to click on the domain names to view the current IPs blocked. The links aren't really distinguishable from the text in the default skin)