HTTP Server Prone To Slow Denial Of Service Attack

1. For Apache HTTPD Server:
Upgrade to the latest version that has "mod_reqtimeout" module support available by default.
Then enable the module "mod_reqtimeout" and configure it to set the timeout and minimum data rate for receiving requests,

See my screenshot below

RequestReadTimeout header=10-20,minrate=500
RequestReadTimeout body=10,minrate=500

For a complete write-up see Using mod_reqtimeout to make HTTP Server less vulnerable for DOS Attack for CentOS

References:

1. Apache Module mod_reqtimeout
2. Using mod_reqtimeout to make HTTP Server less vulnerable for DOS Attack for CentOS