Artech House - Voice.over.802.11.pdf - VirtuaLitera

❘❙❚❘❙❚Security and Vo802.11 105Vo802.11 phone802.11 access point❘❙❚❘❙❚Authentication requestAuthentication responseFigure 7.5Open system authentication in an 802.11 network.it is possible for an attacker to simulate the wireless network and get users toconnect to it and to reveal additional information useful to the attacker.MAC address filtering is sometimes used to control access to resources.However, MAC address filtering is not adequate for authentication of users. It isrelatively simple to sniff valid MAC addresses out of the air and change theMAC address of a client card to masquerade as a legitimate user. Once access isgained to the network, all computers on the network are accessible becauseWEP and 802.11 do not provide access control mechanisms to limit whichresources can be accessed. In a home, SOHO, or small business environment,this may not be an issue. However, in an enterprise environment, it may beimportant to control access to resources based on access policies.Examples of FabricationMan-in-the-Middle AttacksTo execute a man-in-the-middle attack, two hosts must be convinced that thecomputer in the middle is the other host. The classic version of this attackStationAccess pointAuthenticationrequestChallenge textChallenge response(Encrypted challenge text)ConfirmsuccessFigure 7.6 Shared key authentication in an 802.11 network. (From: [4]. © 2000 Intel Corporation.Reprinted with permission.)