Wi-Fi Technology

Agenda

Introduction

Wi-Fi Technologies

Wi-Fi Architecture

Wi-Fi Network Elements

How a Wi-Fi Network Works

Wi-Fi Network Topologies

Wi-Fi Configurations

Applications of Wi-Fi

Wi-Fi Security

Advantages/ Disadvantages of Wi-Fi

Introduction

• Wireless Technology is an alternative to WiredTechnology, which is commonly used, forconnecting devices in wireless mode.

• Wi-Fi (Wireless Fidelity) is a generic term thatrefers to the IEEE 802.11 communicationsstandard for Wireless Local Area Networks(WLANs).

• Wi-Fi Network connect computers to each other,to the internet and to the wired network.

The Wi-Fi Technology

Wi-Fi Networks use Radio Technologies totransmit & receive data at high speed:

IEEE 802.11b

IEEE 802.11a

IEEE 802.11g

IEEE 802.11b

• Appear in late 1999

• Operates at 2.4GHz radio spectrum

• 11 Mbps (theoretical speed) - within 30 m Range

• 4-6 Mbps (actual speed)

• 100 -150 feet range

• Most popular, Least Expensive

• Interference from mobile phones and Bluetooth

devices which can reduce the transmission

speed.

IEEE 802.11a

• Introduced in 2001

• Operates at 5 GHz (less popular)

• 54 Mbps (theoretical speed)

• 15-20 Mbps (Actual speed)

• 50-75 feet range

• More expensive

• Not compatible with 802.11b

Access point

Adapters

Components of Wi-Fi

Wi-Fi Antenna

Wi-Fi Bridge

PCI cards that accept wireless PC cards

External USB wireless NICs

How a Wi-Fi Network Works

• Basic concept is same as Walkie talkies.

• A Wi-Fi hotspot is created by installing an access point

to an internet connection.

• An access point acts as a base station.

• When Wi-Fi enabled device encounters a hotspot the

device can then connect to that network wirelessly.

• A single access point can support up to 30 users and

can function within a range of 100 – 150 feet indoors and

up to 300 feet outdoors.

• Many access points can be connected to each other via

Ethernet cables to create a single large network.

Wi-Fi Network Topologies

• AP-based topology (Infrastructure Mode)

• Peer-to-peer topology (Ad-hoc Mode)

• Point-to-multipoint bridge topology

AP-based topology

• The client communicate through Access Point.

• BSA-RF coverage provided by an AP.

• ESA-It consists of 2 or more BSA.

• ESA cell includes 10-15% overlap to allow

roaming.

Peer-to-peer topology

• AP is not required.

• Client devices within

a cell can

communicate directly

with each other.

• It is useful for setting

up of a wireless

network quickly and

easily.

Point-to-multipoint bridge topology

This is used to connect a LAN in one building to a LANs

in other buildings even if the buildings are miles

apart.These conditions receive a clear line of sight

between buildings. The line-of-sight range varies based

on the type of wireless bridge and antenna used as well

as the environmental conditions.

Wi-Fi Configurations

Wi-Fi Configurations

Wi-Fi Configurations

Wi-Fi communication

Wi-Fi Applications

• Home

• Small Businesses or SOHO

• Large Corporations & Campuses

• Health Care

• Wireless ISP (WISP)

• Travellers

Wi-Fi Security Threats

• Wireless technology doesn’t remove any

old security issues, but introduces new

ones

• Eavesdropping

• Man-in-the-middle attacks

• Denial of Service

Eavesdropping

• Easy to perform, almost impossible to detect

• By default, everything is transmitted in clear text

• Usernames, passwords, content ...

• No security offered by the transmission medium

• Different tools available on the internet

• Network sniffers, protocol analysers . . .

• Password collectors

• With the right equipment, it’s possible to

eavesdrop traffic from few kilometers away

MITM Attack

1. Attacker spoofes a disassociate message from the victim

2. The victim starts to look for a new access point, and the attacker advertises his own AP on a different channel, using the real AP’s MAC address

3. The attacker connects to the real AP using victim’s MAC address

Denial of Service

• Attack on transmission frequecy used

• Frequency jamming

• Not very technical, but works

• Attack on MAC layer

• Spoofed deauthentication / disassociation messages

• can target one specific user

• Attacks on higher layer protocol (TCP/IP protocol)

• SYN Flooding

Wi-Fi Security

The requirements for Wi-Fi network

security can be broken down into two

primary components:

• Authentication

User Authentication

Server Authentication

• Privacy

Authentication

• Keeping unauthorized users off the network

• User Authentication

• Authentication Server is used

• Username and password

• Risk:

• Data (username & password) send before secure channel

established

• Prone to passive eavesdropping by attacker

• Solution

• Establishing a encrypted channel before sending username

and password

Authentication (cont..)

• Server Authentication

• Digital Certificate is used

• Validation of digital certificate occurs

automatically within client software

Wi-Fi Security Techniques

• Service Set Identifier (SSID)

• Wired Equivalent Privacy (WEP)

• 802.1X Access Control

• Wireless Protected Access (WPA)

• IEEE 802.11i

Service Set Identifier (SSID)

• SSID is used to identify an 802.11 network

• It can be pre-configured or advertised in

beacon broadcast

• It is transmitted in clear text

• Provide very little security

Wired Equivalent Privacy (WEP)

• Provide same level of security as by wired network

• Original security solution offered by the IEEE 802.11

standard

• Uses RC4 encryption with pre-shared keys and 24 bit

initialization vectors (IV)

• key schedule is generated by concatenating the shared

secret key with a random generated 24-bit IV

• 32 bit ICV (Integrity check value)

• No. of bits in keyschedule is equal to sum of length of

the plaintext and ICV

Wired Equivalent Privacy (WEP)

(cont.)• 64 bit preshared key-WEP

• 128 bit preshared key-WEP2

• Encrypt data only between 802.11 stations.once it enters

the wired side of the network (between access point)

WEP is no longer valid

• Security Issue with WEP

• Short IV

• Static key

• Offers very little security at all

802.1x Access Control

• Designed as a general purpose network access control mechanism

• Not Wi-Fi specific

• Authenticate each client connected to AP (for WLAN) or switch port(for Ethernet)

• Authentication is done with the RADIUS server, which ”tells” theaccess point whether access to controlled ports should be allowedor not

• AP forces the user into an unauthorized state

• user send an EAP start message

• AP return an EAP message requesting the user’s identity

• Identity send by user is then forwared to the authentication server by AP

• Authentication server authenticate user and return an accept or rejectmessage back to the AP

• If accept message is return, the AP changes the client’s state toauthorized and normal traffic flows

802.1x Access Control

Wireless Protected Access (WPA)

• WPA is a specification of standard based, interoperable securityenhancements that strongly increase the level of data protection andaccess control for existing and future wireless LAN system.

• User Authentication• 802.1x

• EAP

• TKIP (Temporal Key Integrity Protocol) encryption• RC4, dynamic encryption keys (session based)

• 48 bit IV

• per packet key mixing function

• Fixes all issues found from WEP

• Uses Message Integrity Code (MIC) Michael• Ensures data integrity

• Old hardware should be upgradeable to WPA

Wireless Protected Access (WPA)(cont.)

• WPA comes in two flavors

• WPA-PSK • use pre-shared key

• For SOHO environments

• Single master key used for all users

• WPA Enterprise• For large organisation

• Most secure method

• Unique keys for each user

• Separate username & password for each user

WPA and Security

• Data is encrypted• Protection against eavesdropping and man-in-the-

middle attacks

• Denial of Service• Attack based on fake massages can not be used.

• As a security precaution, if WPA equipment seestwo packets with invalid MICs within a second, itdisassociates all its clients, and stops all activity fora minute

• Only two packets a minute enough to completelystop a wireless network

Threats

802.11i

• Provides standard for WLAN security

• Authentication

• 802.1x

• Data encryption

• AES protocol is used

• Secure fast handoff-This allow roamingbetween APs without requiring client tofully reauthenticate to every AP.

• Will require new hardware

Advantages

• Mobility

• Ease of Installation

• Flexibility

• Cost

• Reliability

• Security

• Use unlicensed part of the radio spectrum

• Roaming

• Speed

Limitations

• Interference

• Degradation in performance

• High power consumption

• Limited range