This report, will show by demonstration with Network Penetration, how to reveal security holes by using the same methods as an outside attack and carry out attacks against wired and wireless networks when it comes to sniffing user traffic, abuse VLAN, cracking password, WEP, WPA/WPA2, hacking WPS and analysing traffic. The tests was performed at the Halmstad University with lab equipment and at home with own equipment. Using Backtrack 5 R3 which is compatible with Linux, performance of the tests could be done by making use of various tools that comes with Backtrack.The goal of the project was to demonstrate how to reveal security holes by using the same methods as an outside attack. By testing, demonstrate and report the security of wired and wireless network, the achievement of these goals could be done and a greater insight into network security was gained, which gives more experience and knowledge that can be taken to a future professional life. The results show how simple it can be to abuse a network or sniff a password if there is no attention to the safety and the security configurations that can be implemented.In other words, during this project, both learning and demonstration has been done to show how vulnerable individuals, civilians and entrepreneurs are. It is easier than someone can imagine to obtaining unauthorized information that nobody wants to share out.