Firewall penetration testing is a huge part of the penetration testing process, and sometimes the first step of the process. Penetration testing your firewall plays a big role in black box penetration testing. Just like any attacker, pen testers first test to see how strong your firewall is and try to determine if there is sensitive data (OS, ports, applications, location and personal information). If your system can disclose this information easily it makes you a very vulnerable target, one likely to be attacked. Some information will make you more vulnerable than others, for example if an attacker can acquire your accurate system billing info it could lead to a social engineering attack. Or let’s say your system firewall is disclosing a port that is usually used by a common web application, an attacker can distinguish the web application and run a web application exploit to compromise your system.
There are many free simple public security scanners made for network exploration and firewall penetration testing. One tool I highly suggest is Nmap. Not only is Nmap free, it is also open source and can be scripted for your penetration testing needs. This tool is supported in multiple Linux operating systems and in Microsoft Windows with either GUI friendly interface or command line base. It has many features such as port scanning using UDP and TCP, with a dump of ports from victim’s system, which is beneficial for determining what web applications and services are running. An attacker with knowledge of a web application could dork code for the location. Nmap also protects against OS fingerprinting, which is the capability to determine the target’s operating system (including version detection), which is beneficial for an attacker for obvious reasons, but for your sake as well for setting up a foolproof firewall. When an attacker has found a vulnerability in your system, knowing the operating system is very helpful for exploiting any vulnerabilities (buffer overflows, format-string). Nmap works with popular debugging tools (Nping ,Ncat, Ndiff) for maximum performance and capability.
There are many great tools out there to determine your firewall penetration status, I would highly advise you to test your own system to see how vulnerable your firewall stands. If you are seeking to have a fool proof firewall, or want any kind of penetration testing service contact: Caliber Security Partners, for your security solution.