This plugin allows you to have a simple rate limit option to protect the site against DDoS or brute force attacks. It is suitable to Prevent against IP Stresser and booter scripts that want to increase the consumption of your site's resources with a "Slow" method.
Added:
First, you need to download the plugin from the source (which will be a zip file). Next, you need to go to WordPress admin area and visit Plugins » Add New page. After that, click on the ‘Upload Plugin’ button on top of the page. This will reveal the plugin upload form. Here you need to click on the ‘Choose File’ button and select the plugin file you downloaded earlier to your computer. After you have selected the file, you need to click on the ‘Install Now’ button. Once installed, you need to click on the Activate Plugin link to start using the plugin.
To Prevent against DDoS attacks, you will need an DDoS Protection Service, This plugin may not be effective against large attacks.