In this thesis we deal with security, penetration testing and different types of attacks on wireless networks. We theoretically familiarize with the field of wireless networks, security mechanisms and the most used security standards. Then we systematically overview the field of penetration testing. We divide the penetration testing on types and different methodologies. We explain the tasks of the provider and the subscriber in penetration testing. Description of the process of conducting the penetration testing is made using NIST methodology on the target system and wireless network. Then we focus our attention on known attacks on wireless networks. We learn about the theoretical part of security authentication and the vulnerabilities of wireless networks. The attacks are also practically executed on our own devices.