Wireless Network Flashcards
IBSS
Independent Basic Service Set
Contains only devices/clients with no AP
Ad-hoc WLAN
BSS
Basic Service Set
One AP connected to Network
ESS
Extended Service Set
Multiple APs to provide coverage
DSSS
Direct-Sequence Spread Spectrum
▪ Modulates data over an entire range of frequencies using a series of signals known as chips
▪ More susceptible to environmental interference
▪ Uses entire frequency spectrum to transmit
FHSS
Frequency-Hopping Spread Spectrum (FHSS)
▪ Devices hop between predetermined frequencies
▪ Increases security as hops occur based on a common timer
OFDM
Orthogonal Frequency Division Multiplexing (OFDM)
▪ Uses slow modulation rate with simultaneous transmission of data over 52 data streams
▪ Allows for higher data rates while resisting interference between data streams
RFI
Radio Frequency Interference (RFI)
▪ Caused by using similar frequencies to WLAN ▪ Common sources of interference:
● Other wifi devices (overlapping channels)
● Cordless phones and baby monitors (2.4 GHz)
● Microwave ovens (2.4 Ghz)
● Wireless security systems (2.4 GHz)
● Physical obstacles (Walls, appliances, cabinets)
● Signal strength (Configurable on some devices)
CSMA/CA
Carrier Sense Multiple Access/Collision Avoidance
▪ WLAN uses CSMA/CA to control access to medium, where wires Ethernet uses CSMA/CD
▪ Listens for transmission to determine if safe to transmit
● If channel is clear, transmits Request to Send (RTS)
● Device waits for acknowledgment
● If received an RTS, responds with Clear to Send (CTS)
● If not received, device starts random back off timer
WEP
Wired Equivalent Privacy ▪ Original 802.11 wireless security standard
● Claimed to be as secure as wired networks
▪ Static 40-bit pre-shared encryption key
● Upgraded to 64-bit and 128-bit key over time ▪ Uses 24-bit Initialization Vector (IV)
● Sent in clear text
WPA
Wi-Fi Protected Access (WPA) ▪ Replaced WEP and its weaknesses ▪ Temporal Key Integrity Protocol (TKIP)
● 48-bit Initialization Vector (IV) instead of 24-bit IV
● Rivest Cipher 4 (RC4) used for encryption ▪ Uses Message Integrity Check (MIC)
● Confirms data was not modified in transit ▪ Enterprise Mode WPA
● Users can be required to authenticate before exchanging keys
● Keys between client and AP are temporary
WPA2
CCMP for authentication
AES for encryption
- 128-bit key or above
802.1x
Network Authentication 802.1x
▪ Each wireless user authenticates with their own credentials
▪ Used also in wired networks
EAP
Extensible Authentication Protocol (EAP)
▪ Authentication performed using 802.1x
▪ EAP-FAST
● Flexible Authentication via Secure Tunneling
▪ EAP-MD5
▪ EAP-TLS
NAC
Network Admission Control (NAC)
▪ Permits or denies access to the network based on characteristics of the device instead of checking user credentials
▪ Conducts a posture assessment of client
● Checks the OS and antivirus version of client
