The use of protection in wireless networks is a very important subject. Because of all the benefits that wireless networks provide, they are rapidly spreading and becoming more popular, so their conservation is a very serious problem. For all of these reasons it is very important to pay attention to their safety. When deploying a wireless network we question its safety. It is therefore necessary to choose the equipment and methods that will protect them on a high level. In this paper the theoretical basis discuss the three main methods for protecting wireless networks, WEP, WPA and WPA2. The aspects of authentication, encryption and security are lengthily explained within each method. Besides the theoretical basis, the field survey was conducted in 10 cities on the territory of Croatia. Measurements were conducted using inSSIDer tool, which was main software in the preparation of this paper. After conducting all the measurements, they were analyzed. Results are presented graphically, in tabular and explained lengthily. Besides the great progress, there remains a large problem with security in wireless networks due the poor use of WPA and WPA2 protocols. Except that, a big problem is a very large number of unprotected networks or networks that use WEP protocol. The reason for this is computer illiterate users and their irresponsible and careless behavior.