CEH Certified Ethical Hacker All-in-One Exam Guide by Matt Walker

Author:Matt Walker
Language: eng
Format: epub, mobi
Publisher: McGraw-Hill Education
Published: 2022-09-15T00:00:00+00:00

Figure 7-1 Wireless antennas

NOTE A Yagi antenna is merely a type of directional antenna. However, its name is used for certain directional antennas similar to how “Coke” is used a lot in the South to indicate soda in general.

Other antennas you can use are dipole and parabolic grid. Dipole antennas have two signal “towers” and work omnidirectionally. Parabolic grid antennas are one type of directional antenna and work a lot like satellite dishes. They can have phenomenal range (up to 10 miles due to their power output) but aren’t in use much. Another directional antenna type is the loop antenna, which looks like a circle.

So, you’ve installed a wireless access point and created a network for clients to connect to. To identify this network to clients who may be interested in joining, you’ll need to assign a service set identifier (SSID). The SSID is not a password and provides no security at all for your network. It is simply a text word (32 characters or less) that identifies your wireless network. SSIDs are broadcast by default and are easily obtainable even if you try to turn off the broadcast (in an effort dubbed “SSID cloaking”). The SSID is part of the header on every packet, so its discovery by a determined attacker is a given, and securing it is virtually a moot point.

EXAM TIP If you see a question on wireless security, you can ignore any answer with SSID in it. Remember that SSIDs do nothing for security, other than identify which network you’re on. Encryption standards, such as WEP and WPA, and physical concerns, such as the placement of APs and antennas used, are your security features.

Once the AP is up and a client comes wandering by, it’s time to authenticate so an IP address can be pulled. Wireless authentication can happen in more than a few ways, from simple to complicated, but for study purposes there are three main methods you should look at: Open System Authentication, Shared Key Authentication, and Centralized Authentication (for example, RADIUS). In Open System Authentication, a client can simply send an 802.11 authentication frame with the appropriate SSID to an AP and have it answer with a verification frame. In Shared Key Authentication, the client participates in a challenge/request scenario, with the AP verifying a decrypted “key” for authentication. Both methods serve the purpose of proving you belong to the network and are illustrated in Figure 7-2.

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