Main goals of this diploma thesis is to chart methods used to secure wireless internet networks a test those methods through attack on access point of wireless network with target to receive password to access this network and decryption of captured packets. For charting of types of security measures used for wireless network, I performed a series of measurements in field on different places in Czech Republic and Germany. Primary purpose of mesurements performed in Germany is caomparison of results from Germany with results from Czech Republic. Also, I tried to crack the security measures i controlled environment. Due to illegality of this experiment I used my own network and network that belongs o one of my friends who agreed with the expe...