WAF or Web application firewall is a
security tool that protects a website from various type of attacks
which included but not limited to: SQL-injection, XSS, Local file
inclusion and others. Web based IPS (intrusion prevention system) has
also been designed to protect a web server but these is a difference
between WAF and IPS; web application firewall provides protection
from web-based attack while IPS protect a web server from network
based attack.

The responsibility of a penetration tester is to protect the web server from both directional attacks, so
IPS and WAF are both have their own importance for a pen tester. In
order to conduct a successful vulnerability assessment on a website,
you need to find the security tools that are protecting it.

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    WAFW00F – Web Application Firewall Detection Tool
   
    By Sandro Gauci && Wendel G. Henrique

Usage: wafw00f url1 [url2 [url3 … ]]
example: wafw00f http://www.victim.org/

Options:
  -h, –help            show this help message and exit
  -v, –verbose         enable verbosity – multiple -v options increase
                        verbosity
  -a, –findall         Find all WAFs, do not stop testing on the first one
  -r, –disableredirect
                        Do not follow redirections given by 3xx responses
  -t TEST, –test=TEST  Test for one specific WAF
  -l, –list            List all WAFs that we are able to detect
  –xmlrpc              Switch on the XML-RPC interface instead of CUI
  –xmlrpcport=XMLRPCPORT
                        Specify an alternative port to listen on, default 8001
  -V, –version         Print out the version

Everything has its limitation, wafw00f has also some limitation. It can only detect the firewalls which are listed in the script database, so it is recommended that you should update your tool. In the following example you can see that the firewall name was not fetched by wafw00f.