Free CCNA Wirless Tutorial



Posted: Saturday, January 10, 2009

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Because wireless networks can be accessed by anyone with a compatible wireless network adapter, most models of wireless network adapters and WAPs provide for encryption options. Some devices with this feature enable you to set a security code known as an SSID on the wireless devices on your network. This seven-digit code prevents unauthorized users from accessing your network and acts as an additional layer of security along with your normal network authentication methods, such as user passwords. Other wireless network adapters and WAPs use a list of authorized MAC numbers to limit access to authorized devices only.

All Wi-Fi products support at least 40-bit encryption through the wired equivalent privacy (WEP) specification, but the minimum standard on newer products is 64-bit WEP encryption. Many vendors also offer 128-bit or 256-bit encryption on some of their products. However, the WEP specification is insecure. It is vulnerable to brute-force attacks at shorter key lengths, and it is also vulnerable to differential cryptanalysis attacks, which is the process of comparing an encrypted text with a known portion of the plain text and deriving the key by computing the difference between them. Because WEP encrypts TCP headers, hackers know what the headers should contain in many cases, and they can attempt to find patterns in a large body of collected WEP communications in order to decrypt the key. The attack is complex and difficult to automate, so it is unlikely to occur for most networks, especially at key lengths greater than 128

bits. Furthermore, WEP does not prevent an intruder from attaching a hidden WAP on the network and using it to exploit the network.

New network products introduced in 2003 and beyond now incorporate a new security standard known as Wi-Fi Protected Access (WPA). WPA is derived from the developing IEEE 802.11i security standard, which will not be completed until mid-decade. WPA-enabled hardware works with existing WEP-compliant

devices, and software upgrades might be available for existing devices.

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