WLANs use air as a medium for transferring data between users. This medium permits the hackers listening and sniffing the transferred data from away distance without the need for a real physical connection. In this paper, the threats of different security levels, such as SSID, MAC filter, and WPA II used to ensure protection of WLANs are investigated. The structure and fundamental concept of every security mechanism are analyzed and discussed. The penetration test for cryptanalysis WPA II in the PSK mode, discovering hidden SSID, and bypassing MAC filter is illustrated experimentally. The assessment process is executed using the Kali Linux platform and many other tools.