Wireless Networks Flashcards
wap
Wireless Access Point
Expands wired LAN into the wireless domain
All clients on an access point are on a single collision domain
(IBSS)
Independent Basic Service Set
contains only devices/clients with no access point (ad hoc)
(BSS)
Basic Service Set
only one access point connected to the network
ex: small office/home office
(ESS)
Extended Service Set
contains multiple access points to provide coverage
ex: college
Wireless Mesh Topology
May not use a centralized control
Range of combined wireless tech: WiFi, Microwave, Cellular etc …
Access Point Placement
Careful planning is required to prevent the APs from interfering with one another and still maintaining the desired coverage area
Coverage should overlap between APs to allow uninterrupted roaming from one
cell to another but can’t use overlapping frequencies
AP Placement (2.4 Ghz)
Non-overlapping coverage cells for 2.4 GHz band should have 10% to 15% coverage overlap in
coverage area
AP Placement (5 Ghz)
Identical channels should be separated by at least two cells instead of
one
Site Surveys
Wireless survey to determine coverage areas
Produces a heat map with coverage
Omnidirectional Antenna
radiates power equally all directions
Unidirectional Antenna
focuses power in one direction for covering greater distances
ex: yagi
Spread Spectrum Wireless Transmissions
Direct-Sequence Spread Spectrum (DSSS)
Orthogonal Frequency-Division Multiplexing (OFDM)
Frequencies and Channels
2.4 GHz band: Channels 1, 6, and 11 will avoid overlapping frequencies in 2.4 GHz band
5 GHz band: channel bonding
Channel Bonding
Allows you to create a wider channel by merging neighboring channels
into one
make channel size larger, increase speed, increase interferance
802.11
band: 2.4 GHz
bandwidth: 1-2 Mbps
802.11a
band: 5 GHz
bandwidth: 54 Mbps
802.11b
band: 2.4 GHz
bandwidth: 11 Mbps
802.11g
band: 2.4 GHz
bandwidth: 54 Mbps
802.11n
band: 2.4 and 5 GHz
bandwidth: >300Mbps
MIMO, channel bonding
802.11ac
band: 5 GHz
bandwidth: 3 Gbps
MU-MIMO
802.11ax
band: 2.4 5, 6GHz
bandwidth: 9.6 Gbps
MU-MIMO
MIMO
multiple antennas to receive/send more data
(RFI)
Radio Frequency Interference
Caused by using similar frequencies to WLAN
Other wifi devices (overlapping channels)
Pre-Shared Key
Both AP and client uses same encryption key
bad:
Scalability is difficult if key is compromised
All clients must know the same password
wep
Wired Equivalent Privacy
weak
Uses 24-bit Initialization Vector (IV) sent in clear
Brute Force Attack within minutes using AirCrack-ng and other tools
open
no security
(WPA)
Wi-Fi Protected Access
weak
TKIP used for 48bit IV
RC4 used for encryption
(WPA2)
Wi-Fi Protected Access 2
strong and modern
CCMP for integrity checks
AES for encryption
802.1x
network authentications
wlan: Each wireless user authenticates with their own credentials
(EAP)
Extensible Authentication Protocol
Authentication performed using 802.1x
EAP-FAST, EAP-MD5, EAP-TLS
(NAC)
Network Admission Control
Permits or denies access to the network based on characteristics of the
device OS, anti virus
Captive Portals
Web page that appears before the user is able to access the network
resources
Geofencing
GPS or RFID defines real-world boundaries
Device can send alerts if it leaves area
Network authentication can use it to determine access
Disable SSID Broadcast
Configures an AP to not broadcast the name of the wireless LAN
but, Knowledgeable users can still easily find the SSID using wireless
sniffing tools
Rogue Access Point
Malicious users set up an AP to lure legitimate users to connect to the AP
then capture all the packets (data)
Unsecured Wireless Networks
War Driving: Occurs when users perform reconnaissance looking for unsecured wireless networks
War Chalking: Occurs when users write symbols on a wall to notify others of AP characteristics
