SlowHTTPTest is a highly configurable tool that simulates some Application Layer Denial of Service attacks. 
It works on majority of Linux platforms, OSX and Cygwin - a Unix-like environment and command-line interface 
for Microsoft Windows.

It implements most common low-bandwidth Application Layer DoS attacks, such as slowloris, Slow HTTP POST, 
Slow Read attack (based on TCP persist timer exploit) by draining concurrent connections pool, as well
as Apache Range Header attack by causing very significant memory and CPU usage on the server.

Slowloris and Slow HTTP POST DoS attacks rely on the fact that the HTTP protocol, by design, requires 
requests to be completely received by the server before they are processed. If an HTTP request is not 
complete, or if the transfer rate is very low, the server keeps its resources busy waiting for the 
rest of the data. If the server keeps too many resources busy, this creates a denial of service. 
This tool is sending partial HTTP requests, trying to get denial of service from target HTTP server.

Slow Read DoS attack aims the same resources as slowloris and slow POST, but instead of prolonging
the request, it sends legitimate HTTP request and reads the response slowly. 

DISCLAIMER: Keep in mind that slowhttptest is of little use as a script kiddie tool. It cannot
be pointed blindly at arbitrary targets, like e.g. LOIC.  Rather, where it excels is in its
breadth of attack options, high customizability and its in-depth analytics. As such, it will be
mostly useful for server administrators trying to stress test their systems.