It has been possible to do penetration testing using your Pi for some time now, particularly with Kali Linux. However, it has now been made even simpler with a set of scripts known as Warberry Pi. The set of scripts runs when you plug in an Ethernet cable and collects as much information as it can about your network. You can then get the data off via SSH or by looking at the Pi directly. Full instructions and all the code can be found on GitHub.