Securing Wireless LANs A Practical Guide for

Wireless LANs will enable small teams and communities to communicate via their mobile devices without cables. This new technology will facilitate communication in small businesses/teams such as in hospitals, on construction sites, warehouses, etc. Held provides a comprehensive guide to the implementation, planning and monitoring of all aspects of wireless LAN security in small offices/small to medium business (SMBs). Securing Wireless LANs is timely in addressing the security issues of this important new technology and equips its readers with the tools they need to make the appropriate choice for their own situation. This ideal introduction to wireless LAN technology: Provides a broad overview of all the different issues and practical guidance of how to make wireless LANs secure at home as well as in small offices Explains how to monitor wireless LANs, configure different types of wireless equipment Discusses which technologies are best for different situations and requirements Gives practical hints and advice on how to implement them

<b>Gilbert Held</b> is an internationally known award-winning author and teacher with over 30 years experience in managing communications networks.

Preface

xv

Acknowledgements

xvii

Chapter 1 Introduction to Wireless LANs

1

(34)

1.1 SECURING THE INSECURE

2

(5)

1.1.1 AAE AND A FUNCTIONS

2

(1)

1.1.2 AUTHENTICATION

2

(1)

1.1.3 AUTHORIZATION

3

(1)

1.1.4 ENCRYPTION

3

(1)

1.1.5 ACCOUNTING

4

(1)

1.1.6 PRACTICAL NETWORK PROTECTION METHODS

4

(3)

1.2 NETWORK ARCHITECTURE

7

(20)

1.2.1 BASIC NETWORKING DEVICES

7

(1)

1.2.2 THE WIRELESS LAN STATION

8

(2)

1.2.3 THE ACCESS POINT

10

(3)

1.2.4 THE WIRELESS BRIDGE

13

(1)

1.2.5 THE WIRELESS ROUTER

13

(5)

1.2.6 THE BASIC SERVICE SST

18

(2)

1.2.7 THE EXTENDED SERVICE SET (ESS)

20

(1)

1.2.8 STATION SERVICES

21

(6)

1.3 IEEE WIRELESS LAN STANDARDS

27

(5)

1.3.1 THE BASIC IEEE 802.11 STANDARD

28

(2)

1.3.2 802.11B

30

(1)

1.3.3 802.11A

30

(1)

1.3.4 802.11C

30

(1)

1.3.5 802.11D

31

(1)

1.3.6 802.11E

31

(1)

1.3.7 802.11E

31

(1)

1.3.8 802.11G

31

(1)

1.3.9 802.11H

31

(1)

1.3.10 802.11I

32

(1)

1.4 BOOK PREVIEW

32

(3)

1.4.1 FRAME FORMATS AND BASIC SECURITY OPERATIONS

32

(1)

1.4.2 UNDERSTANDING WIRELESS SIGNALS

33

(1)

1.4.3 UNDERSTANDING WEP

33

(1)

1.4.4 SECURITY RISKS

33

(1)

1.4.5 PROPRIETARY SECURITY ENHANCEMENT TECHNIQUES

33

(1)

1.4.6 STANDARDS BASED SECURITY

34

(1)

Chapter 2 Frame Formats and Basic Security Operation

35

(26)

2.1 FRAME FORMATS

35

(18)

2.1.1 BASIC FRAME FORMAT

36

(1)

2.1.2 FRAME CONTROL FIELD

36

(7)

2.1.3 CONTROL FRAMES

43

(3)

2.1.4 MANAGEMENT FRAMES

46

(7)

2.1.5 THE AUTHENTICATION PROCESS

53

(1)

2.2 WEP AND PRIVACY

53

(8)

2.2.1 MISCONCEPTIONS

53

(1)

2.2.2 DEVELOPMENT CONSTRAINTS

54

(4)

2.2.3 DEFICIENCIES

58

(3)

Chapter 3 Understanding Wireless Signals

61

(24)

3.1 THE WIRELESS RF SPECTRUM AND BASIC MEASUREMENTS

62

(9)

3.1.1 FREQUENCY

62

(1)

3.1.2 PERIOD AND WAVELENGTH

63

(1)

3.1.3 BANDWIDTH

64

(1)

3.1.4 THE FREQUENCY SPECTRUM

64

(2)

3.1.5 POWER MEASUREMENTS

66

(3)

3.1.6 POWER LEVEL

69

(1)

3.1.7 SIGNAL-TO-NOISE RATIO

69

(2)

3.2 ANTENNA BASICS

71

(14)

3.2.1 BASIC OPERATION

72

(1)

3.2.2 CATEGORIES

73

(1)

3.2.3 ANTENNA GAIN

73

(1)

3.2.4 DIRECTIONALITY AND EIRP

74

(1)

3.2.5 POWER LEVELS

74

(1)

3.2.6 PROPAGATION LOSS

75

(1)

3.2.7 INCREASING ANTENNA GAIN

76

(1)

3.2.8 POWER LIMITS

77

(1)

3.2.9 RECEIVER SENSITIVITY

78

(1)

3.2.10 REDUCING EMITTED RADIATION

79

(1)

3.2.11 HORIZONTAL TRANSMISSION DISTANCE

80

(1)

3.2.12 EQUIPMENT POSITIONING

81

(2)

3.2.13 USING MONITORING EQUIPMENT

83

(2)

Chapter 4 Understanding WEP

85

(28)

4.1 THE WEP FRAME BODY

86

(5)

4.1.1 THE IV

86

(1)

4.1.2 THE ICV

87

(1)

4.1.3 THE NAKED DEFAULT

87

(3)

4.1.4 WEP KEY LIMITATIONS

90

(1)

4.2 LOCATING AND OBSERVING WIRELESS LAN TRAFFIC

91

(6)

4.2.1 NETWORK STUMBLER

91

(2)

4.2.2 MONITORING WITH AIROPEEK

93

(4)

4.3 RC4

97

(5)

4.3.1 OVERVIEW

97

(1)

4.3.2 OPERATION

98

(1)

4.3.3 ILLUSTRATIVE EXAMPLE

99

(3)

4.3.4 STRENGTHS AND WEAKNESSES

102

(1)

4.4 WEP WEAKNESS

102

(11)

4.4.1 UNSAFE AT ANY SIZE

102

(1)

4.4.2 THE INSECURITY OF 802.11

103

(4)

4.4.3 EXPLOITING RC4 WEAKNESS

107

(1)

4.4.4 BREAKING WEP

108

(1)

4.4.5 AIRSNORT

109

(1)

4.4.6 WEPCRACK

110

(3)

Chapter 5 Security Risks and Countermeasures

113

(36)

5.1 The SSID

113

(4)

5.1.1 OVERVIEW

114

(1)

5.1.2 OVERRIDING THE SSID

114

(1)

5.1.3 OBTAINING THE SSID

115

(2)

5.1.4 COUNTERMEASURES

117

(1)

5.2 EAVESDROPPING

117

(4)

5.2.1 OVERVIEW

117

(1)

5.2.2 THREATS

118

(1)

5.2.3 COUNTERMEASURES

118

(3)

5.3 MASQUERADE

121

(3)

5.3.1 OVERVIEW

121

(1)

5.3.2 COUNTERMEASURES

122

(2)

5.4 DATA MODIFICATION

124

(1)

5.4.1 OVERVIEW

124

(1)

5.4.2 COUNTERMEASURES

124

(1)

5.5 FILE SHARING

124

(7)

5.5.1 OVERVIEW

124

(1)

5.5.2 WINDOWS 95

125

(3)

5.5.3 WINDOWS 2000

128

(3)

5.5.4 COUNTERMEASURES

131

(1)

5.6 JAMMING

131

(2)

5.6.1 OVERVIEW

131

(1)

5.6.2 COUNTERMEASURES

132

(1)

5.7 ENCRYPTION ATTACKS

133

(2)

5.7.1 OVERVIEW

134

(1)

5.7.2 COUNTERMEASURES

135

(1)

5.8 SNMP

135

(6)

5.8.1 CODING FLAWS

136

(1)

5.8.2 SNMP VERSIONS

136

(5)

5.8.3 COUNTERMEASURES

141

(1)

5.9 BROADCAST MONITORING

141

(4)

5.9.1 OVERVIEW

142

(2)

5.9.2 COUNTERMEASURES

144

(1)

5.10 ACCESSING A MANAGEMENT CONSOLE

145

(1)

5.10.1 OVERVIEW

145

(1)

5.10.2 COUNTERMEASURES

145

(1)

5.11 THEFT OF HARDWARE

146

(1)

5.11.1 OVERVIEW

146

(1)

5.11.2 COUNTERMEASURES

146

(1)

5.12 ROGUE ACCESS POINTS

147

(2)

5.12.1 OVERVIEW

147

(1)

5.12.2 COUNTERMEASURES

147

(2)

Chapter 6 Proprietary Security Enhancement Techniques

149

(34)

6.1 MAC ADDRESS AUTHENTICATION

150

(4)

6.1.1 IEEE 802.11 AUTHENTICATION

150

(1)

6.1.2 IMPLEMENTATION METHODS

151

(1)

6.1.3 ACCESS POINT UTILIZATION

151

(1)

6.1.4 USING A RADIUS SERVER

151

(1)

6.1.5 DATAFLOW

151

(1)

6.1.6 LIMITATIONS WHEN USING AN AP

151

(1)

6.1.7 LIMITATIONS USING A RADIUS SERVER

152

(1)

6.1.8 CHAP

153

(1)

6.1.9 VISITOR CONSIDERATIONS

154

(1)

6.2 CLOSED SYSTEM OPTION

154

(1)

6.2.1 OVERVIEW

155

(1)

6.2.2 LIMITATIONS

155

(1)

6.3 SYSTEM ACCESS PASS PHRASE

155

(1)

6.3.1 OVERVIEW

155

(1)

6.3.2 NETWORK ACCESS

156

(1)

6.3.3 LIMITATIONS

156

(1)

6.4 DYNAMIC KEY EXCHANGE AND WEAK KEY AVOIDANCE

156

(2)

6.4.1 DYNAMIC KEY EXCHANGE

157

(1)

6.4.2 OVERVIEW

157

(1)

6.4.3 LIMITATIONS

157

(1)

6.4.4 WEAK KEY AVOIDANCE

158

(1)

6.4.5 OVERVIEW

158

(1)

6.4.6 LIMITATIONS

158

(1)

6.5 PROTECTING WIRELESS CLIENTS FROM THE PUBLIC NETWORK

158

(8)

6.5.1 OVERVIEW

159

(1)

6.5.2 CISCO ACCESS LISTS

159

(2)

6.5.3 SMC NETWORKS BARRICADE PACKET FILTERING

161

(2)

6.5.4 LIMITATIONS

163

(2)

6.5.5 SUMMARY

165

(1)

6.6 ANTENNA ORIENTATION AND SHIELDING

166

(2)

6.6.1 OVERVIEW

166

(1)

6.6.2 ALTERING SIGNAL STRENGTH

166

(1)

6.6.3 LIMITATIONS

167

(1)

6.7 MINIMIZING TRANSMIT POWER AND ANTENNA CONTROL

168

(4)

6.7.1 POWER MANAGEMENT

168

(2)

6.7.2 ANTENNA CONTROL

170

(1)

6.7.3 POWER LEVEL CONTROL

170

(1)

6.7.4 LIMITATIONS

171

(1)

6.8 WIRELESS INTRUSION DETECTION

172

(1)

6.8.1 OVERVIEW

172

(1)

6.8.2 LIMITATIONS

172

(1)

6.9 LEAP

173

(10)

6.9.1 OVERVIEW

173

(1)

6.9.2 OPERATION

174

(1)

6.9.3 CONFIGURATION

174

(1)

6.9.4 CONFIGURING THE ACCESS POINT

175

(1)

6.9.5 CLIENT CONFIGURATION

175

(2)

6.9.6 ENABLING WEP

177

(4)

6.9.7 LIMITATIONS

181

(2)

Chapter 7 Standards Based Security

183

(62)

7.1 THE IEEE 802.1X STANDARD

183

(37)

7.1.1 OVERVIEW

183

(1)

7.1.2 GENERAL OPERATION

184

(1)

7.1.3 DATA FLOW

185

(2)

7.1.4 THE EAP PROTOCOL

187

(1)

7.1.5 MESSAGE TYPES

188

(1)

7.1.6 EAP PACKET FORMAT

188

(1)

7.1.7 THE DUAL-PORT AUTHENTICATION MODEL

189

(1)

7.1.8 SECURITY LIMITATIONS

189

(4)

7.1.9 USING THE CISCO AIRONET 350

193

(1)

7.1.10 CLIENT SETUP

193

(5)

7.1.11 NETWORKSECURITY

198

(2)

7.1.12 USING WINDOWS XP

200

(3)

7.1.13 ACCESS POINT SETUP

203

(6)

7.1.14 SECURITY SETUP

209

(1)

7.1.15 ACCESS

209

(2)

7.1.16 SECURITY SETUP OPTIONS

211

(8)

7.1.17 CLOSING THOUGHTS

219

(1)

7.2 EVOLVING ENCRYPTION

220

(4)

7.2.1 TKIP

221

(1)

7.2.2 AES

222

(2)

7.3 VPNS AND TUNNELING PROTOCOLS

224

(21)

7.3.1 VPN OVERVIEW

224

(1)

7.3.2 NEED FOR SECURITY

225

(1)

7.3.3 TYPES OF VPNS

226

(2)

7.3.4 APPLICABILITY TO WIRELESS LANS

228

(1)

7.3.5 VPN PROTOCOLS

229

(1)

7.3.6 PPTP

229

(3)

7.3.7 L2TP AND IPSEC

232

(2)

7.3.8 VPN OPERATIONS

234

(11)

Appendix A Wireless LAN Security Checklist

245

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Securing Wireless LANs A Practical Guide for Network Managers, LAN Administrators and the Home Office User

Summary

Author Biography

Table of Contents

Supplemental Materials