Currently the mobile wireless technology is experiencing rapid growth. However the major challenge for deployment of this technology with its special characteristics is securing the existing and future vulnerabilities. Major security and privacy issues for standard wireless networks include the authentication of wireless clients and the encryption and data integrity of wireless LANs. Presently techniques are available to address some of these problems, such as cryptography, virtual private networks. Furthermore the recent advances in encryption, public key exchange, digital signatures and the development of related standards have set a foundation for the flourishing usage of mobile and wireless technologies in many areas such as ecommerce. However, security in a network goes way beyond encryption of data. It must include the security of computer systems and networks, at all levels, top to bottom. It is imperative to design network protocols with security considered at all layers as well as to arm the networks’ systems and elements with well designed, comprehensive, and integrated attack defeating policies and devices. A foolproof prevention of attacks is challenging because at best the defensive system and application software may also contain unknown weaknesses and bugs. Thus, early warning systems (i.e. intrusion detection systems) as components of a comprehensive security system are required in order to prime the execution of countermeasures.