This presentation aims at showing WiFi trafic injection applications in order to practically demonstrate weaknesses of commonly deployed WiFi environments, aka WEP or open networks such as hotspots, for network itself and also for stations connected to it. A practical point of vue is adopted instead of giving another "WiFi is insecure" theorical brief. The first part will briefly present 802.11 basics so everyone can understand the whole stuff (management vs. data, how injection works, consequences of injection, etc.) and is ready to understand consequences and thus applications. WiFi adapters, drivers (e.g. hostap) and tools will also be shortly introduced. The second part will develop practical injection cases, with references to existing tools. The very last topic (WiFi stations attacks) will be developped to show how one can just compromise a random host on a WiFi network without even being associated. DoS using management traffic (disassoc, beacons) WEP cracking methods Captive Portal (commercial hotspots) breakthrough WiFi station attacks The third part will focus on how recent protection schemes, aka WPA and WPA2/802.11i, can prevent or mitigate such kind of attacks and give a conclusion to the presentation.