MCSA/MCSE Self-Paced Training Kit (Exam 70-270): Installing ...

Lesson 3 Configuring Wireless Connections
15-35
Typically, the convenience of using SSID broadcasting outweighs the slight security
advantage that disabling broadcasting offers.
Note Several tools exist that can help users locate wireless networks, even if SSID broadcasting
is turned off. As an administrator, you can use these tools to help evaluate the security
of your own wireless network and identify rogue wireless networks in your organization.
Two popular tools include NetStumbler, which you can find at http://www.netstumbler.com,
and AirSnare, which you can find at http://home.comcast.net/~jay.deboer/airsnare.
Wired Equivalent Privacy (WEP)
Wired networks normally require a physical connection in order to be compromised.
In wireless networks, because the data is broadcast using radio, intruders can intercept
the signals. If those signals are not encrypted, intruders can view the data being transmitted.
Wired Equivalent Privacy (WEP) is one of two wireless encryption standards
supported by Windows XP Professional (the other being Wi-Fi Protected Access, which
is covered in the next section). WEP is the encryption standard that is specified by the
IEEE 802.11 standard.
WEP provides encryption services to protect authorized users of a wireless LAN from
eavesdroppers. WEP functions by using a shared key to encrypt packets of data before
transmitting them over a wireless network. This shared key is generated by using
40-bit or 64-bit secret key encryption, and then adding a 24-bit initialization vector (IV)
to the end of that key. The shared key is set in place for a network, but a new IV is generated
randomly for each packet of data that is transmitted over the network.
Unfortunately, WEP is not as strong as its designers had hoped. There are two basic
shortcomings in the standard WEP protocol:
■ Most networks do not change the shared key often because the basic WEP standard
does not provide a way to dynamically assign the shared key to APs and stations.
Instead, administrators must manually enter the shared key.
Note To make cracking WEP more difficult, most AP vendors avoid using a handful of
known-weak IVs that cracking tools specifically look for. When these IVs are disabled (by
default for most up-to-date APs) and 128 bit encryption is used, WEP is actually a very secure
encryption protocol. A newer implementation of WEP, known as Dynamic WEP, is designed to
address the problem with manual entry of the shared key. Although Dynamic WEP is much
more secure than WEP, the newer and stronger WPA standard and the bad reputation that WEP
has gained probably means that Dynamic WEP will not gain wide acceptance.