Syngress - Eleventh Hour Network+ Exam N10-004 Study Guide (11 ...

70 CHAPTER 4 Wireless Networking
site survey uses the same tools an attacker uses, such as a sniffer and a WEP
cracking tool (for 802.11 network site surveys).
Summary of Exam Objectives
WLANs are inherently insecure because of their very nature; the fact that they radiate
radio signals–containing network traffic that can be viewed and potentially
compromised by anyone within range of the signal. With the proper antennas,
the range of WLANs is much greater than is commonly assumed.
There are a number of different types of wireless networks that can be potentially
deployed. These include HomeRF, Bluetooth, 802.11n, 802.11g, 802.11b, and
802.11a networks. The most common type of WLAN in use today is based on the
IEEE 802.11g standard.
The 802.11 standard defines the 64-bit Wired Equivalent Privacy (WEP) protocol
as an optional component to protect wireless networks from eavesdropping. WEP
is insecure because it encrypts well-known and deterministic IP traffic in layer 3,
and it is vulnerable to plaintext attacks. That is, it is relatively easy for an attacker
to figure out what the plaintext traffic is (for example, a DHCP exchange) and
compare that with the ciphertext, providing a powerful clue for cracking the
encryption.
Another problem with WEP is that it uses a relatively short (24-bit) IV to encrypt
the traffic and WEP uses RC4 as the encryption algorithm, which is well known
and recently it was discovered that it uses a number of weak keys. AirSnort
and WEPCrack are well-known open-source tools that exploit the weak key
vulnerability of WEP. The response to the weaknesses in WEP is the use of Wi-
Fi Protected Access (WPA) which has a longer IV, a stronger algorithm, and a
longer key.
MAC filtering is another defensive tactic that can be employed to protect wireless
networks from unwanted intrusion. Only the wireless station that possess
adaptors that have valid MAC addresses are allowed to communicate with the
AP. However, MAC addresses can be easily spoofed and maintaining a list of valid
MAC addresses may be impractical in a large environment.
Top Five Toughest Questions
1. You are a corporate user trying to connect to the company’s wireless network.
When you look at the list of available networks, you do not find the
corporate network listed. What is most likely the cause
A. Wireless is turned off
B. Incorrect mode
C. Beaconing is turned off
D. Interference
2. You are a corporate user trying to connect to the company’s wireless network.
You are within the distance limit of the wireless network yet you