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802.11 Wireless Security
John Berti
Senior Manager
Deloitte Security and Privacy Services
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Agenda
Introduction to WirelessWireless NetworksWireless SecurityTop 8 Security Issues with 802.11Security Controls for Wireless NetworksSummary Best PracticesFinal Thoughts
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Introduction to Wireless
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Cell Phones
PDAs
WLANs
The WirelessWorld
CordlessPhones
Toys
Appliances
Introduction to Wireless
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103 Hz
106 Hz
109 Hz
1012 Hz
1015 Hz
1018 Hz
1021 Hz
Radio
Microwave
Infrared
Visible LightUltraviolet
X-Ray
Gamma Rays
Introduction to Wireless
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The Radio Frequency Band
0 100 200 300 400 500 600 700 800 900 1GHz 3GHz 5GHz 10GHz
AM Radio (5351605 KHz)
VHF TV (174216 MHz)
FM Radio (88108 MHz)
UHF TV (512806 MHz)
Analog Cellular (824-894 MHz)
Digital Cellular (1850-1900 MHz)
Cordless Phones, Toys (900 MHz)
802.11b,g Bluetooth, Phones (2.4 GHz)
802.11a, g (5 GHz)
Unlicensed Radio Frequencies
Licensed Radio Frequencies
Introduction to Wireless
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Wireless Networks
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What is a Wireless Network
Wireless AccessPoint
Demilitarized Zone(Firewall, Web Servers)
Wireless NetworkCard
Wireless Laptop
Wireless Phone
Wireless PDA
InternalNetwork
Internal Network
Wireless Networks
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Wireless Network Standards
Bluetooth Intended as a replacement for cables over shorter
distances, with an effective range of up to 10 meters. 1 Mbps Date Rate 2.4 GHz Frequency Band
802.11b Extension to 802.11 Wireless LAN standard 11 Mbps Data Rate 2.4 GHz Frequency Band Digital Sequence Spread Spectrum (DSSS)
Wireless Networks
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Wireless Network Standards
802.11a Extension to 802.11 Wireless LAN standard 54 Mbps Data Rate 5 GHz Frequency Band Orthogonal Frequency Division Multiplexing (OFDM)
802.11g Replacement for 802.11b with higher rate 54 Mbs Data Rate 2.4 GHz and 5 GHz Frequency Bands
Wireless Networks
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Wireless Networks
802.11 Standards Comparison
WirelessStandard
802.11b 802.11a 802.11g
Popularity Widely Adopted Not Very Popular Widely Adopted
Speed 11 Mbps 54 Mbps 54 Mbps
Cost Inexpensive More Expensive Inexpensive
Frequency 2.4 GHz 5 GHz 2.4 GHz
Range 300 1750 ft 60 100 ft 100 150 ft
Public Access
Hotspots availableat most airports,
colleges and somerestaurants and
coffee shops
NoneHotspots readily
available
Compatibility 802.11b 802.11a802.11b802.11g
Comparison Data From http://www.linksys.com/edu/wirelessstandards.asp
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Wireless Networks
Other task groups:
802.11e Quality of Service802.11n 100mb over Wireless802.11s Mesh Networks (Self Healing)
802.11r Fast Hand-off Re-association from AP toAP
802.11p Wi-Fi in moving vehicles
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Wireless Security
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Wireless Security
There are numerous risks associated with wirelesstechnology that could potentially be detrimental toan organization and its wireless infrastructure.
These risks can be categorized into 6 classes:
Eavesdropping;Transitive Trust;Impersonation or masquerading;Denial of Service;
Infrastructure;Device vulnerability;
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802.1x Access Control Complete and published standard for controlled port access Dynamically generated, session based WEP keys Both session & packet authentication User oriented authentication support Extensible Authentication Protocol (EAP) an extension to
RADIUS servers enabling wireless client authentication to the
wired LAN. Several vendors, like Cisco and 3Com, have already begunmeasures to ensure their implementations comply with thelatest draft of 802.1x standards
802.11i Security
100% focus on security Standard completed Provides extensions to current WEP requirements
Authentication algorithm yet to be determined
Advanced Encryption Standard (AES) - block cipher encryption algorithm
Wireless Security
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Wireless Security
Wired Equivalent Privacy (WEP) is the standard for WLAN encryption It is not widely used (50% of networks dont use it) Easily broken It uses shared keys
For more details on WEP Cracking see the paper by Scott Fluhrer, ItsikMantin, and Adi Shamir.http://www.drizzle.com/%7Eaboba/IEEE/rc4_ksaproc.pdf
Newer WLAN equipment will support Wi-Fi Protected Access (WPA)standards Subset of WLAN security standards based on 802.11i working group
WPA TKIP Changing of keys WPA2 - Advanced Encryption Standard (AES)
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Problems with WEP
1. WEP is hardly used!
In this scan donerecently on my wayto work only 15 ofthe 45 access pointsdetected used WEP.
Thats only 33%.
Note: Some of thesenetworks mayactually use othermethods ofencrypting data such
as VPN
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Problems with WEP
2. WEP Can Be Cracked
The IV is sent as plaintext with the encrypted packet. It can besniffed.
XOR is a simple process that can be easily used to deduce anyunknown value if the other two values are known
The first byte of transmitted data is always the same, giving an
attacker knowledge of both the plaintext and ciphertext.(The SNAP header, which equals AA in hex or 170decimal.)
A certain format of IVs are known to be weak. By targetingattacks on packets with weak IVs the amount of data and analysis
needed to derive the shared key is greatly reduced. By combining the above observations about the implementationof WEP, hackers have developed tools that can obtain the sharedkey after collecting approximately 500,000 to 2,000,000 packetswith < 1 minute cracking time.
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Problems with WEP
3. WEP uses a Shared Key
Using shared keys is impractical on large networks
Key management is very difficult (Difficult to ensure keys can beperiodically changed)
Knowledge of the shared key is disseminated
Inevitably someone will incorrectly configure a wireless device
IndexNetwork
Type ESSIDBSSID (MAC
address) Channel Cloaked WEPDataRate
Max SignalStrength
1 Access Point 00:01:xx:xx:xx:xx 11 No Yes 11 62
2 Access Point 00:01:xx:xx:xx:xx 0 No No 0 69
3 probe wlan 00:01:xx:xx:xx:xx 0 No No 11 71
4 probe wlan 00:01:xx:xx:xx:xx 0 No No 11 73
5 unknown wlan 00:01:xx:xx:xx:xx 0 No No 11 60
6 unknown !OUxxxxxx 00:40:xx:xx:xx:xx 6 No No 11 71
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WPA Security
WiFi Protected Access (WPA) originally a temporary answer to flaws inWEP. At the heart of WPA is TKIP (Temporary Key Integrity Protocol) whichuses re-keying to get away from the problems inherent in static WEP.
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WPA Security
Adds authentication through one of two methods1) Pre-shared Key (PSK), which is similar to WEP, fine for small networks2) 802.1x authentication, uses a backend authentication server such asRADIUS
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Top 8 Security Issues with 802.11
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Detection & Eavesdropping
Detection WLAN will generateand broadcastdetectable radio
waves for a greatdistance
Eavesdropping WLAN signals
extend beyondphysical securityboundaries
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Eavesdropping
Service Set Identifier (SSID) may be broadcasted. SSID string may identify your organization.
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Eavesdropping
Standard Wired Equivalent Privacy (WEP)encryption is often not used. When used, WEP is flawed and vulnerable. No user authentication in WEP.
Clear Text PasswordsIP Addresses
Company Data
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Modification, Injection & Hijacking
Modification Standard Wired Equivalent Privacy (WEP)
encryption has no effective integrity protection. Injection
Static WEP keys can be determined by analysis.
Adversaries can attach to the network withoutauthorization. Hijacking
Adversaries can hijack authenticated sessionsprotected only by WEP.
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Security Architecture
Firewall
Internal Network
Internet
DMZ
WLAN Architecture
Rogue AP
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Wireless LAN Security Controls
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Wireless LAN Security ControlsSubtopics
1. SSID Broadcasting2. MAC Address Filtering3. Security Architecture4. Radio Frequency Management
5. Encryption6. Authentication7. New Wireless LAN Security Protocols
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SSID Broadcasting
Disable the broadcasting of the SSID.Not possible on all Access PointsEasily bypassed
Only useful on low-value networksSSID should also not be easily correlated toyour organization name
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MAC Address Filtering
Some Access Points allow the administratorto specify which link layer (MAC) addressescan attach.
Easily bypassedDoes not scaleOnly useful for low-value networks
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Security Architecture
Firewall
Internal Network
Internet DMZ (VPN Server)
DMZ (VPN Server)
Firewall
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Radio Frequency Management
Building A
Parking Lot
Use a scanner to determine yourRF footprintMonitor interference sources
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Wireless Encryption
Static WEP keys are insufficient for manynetworksNew secure protocols exist for WLANprotection
Layered VPN is a common solution for WLANnetworks
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Subtopics
Wireless LAN Security Mechanisms:
Access Control Authentication Encryption Integrity
802.11 Wireless LAN Security Protocols: 802.1X / Dynamic WEP Wi-Fi Protected Access (WPA) Wi-Fi Protected Access 2 (WPA2)
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Authentication
Wireless LAN needs an authenticated key exchangemechanism
Most secure WLAN implementations use ExtensibleAuthentication Protocol (EAP)
Many EAP methods are availableOne factor include EAP-MD5, LEAP, PEAP-MSCHAP,
TTLS-MSCHAP, EAP-SIMTwo factor methods include EAP-TLS, TTLS withOTP, and PEAP-GTC
Need mutual authentication
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Integrity Protection
WEP has no cryptographically strong integrityprotectionTKIP uses a new Message Integrity Codecalled Michael
CCMP uses AES in CBC-MAC mode
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802.11 Security Solutions
802.1xDynamic WEP
Wi-FiProtectedAccess
Wi-FiProtectedAccess 2
Access Control 802.1X 802.1X or Pre-
Shared Key
802.1X or Pre-
Shared Key
Authentication EAP methods EAP methodsor Pre-SharedKey
EAP methodsor Pre-SharedKey
Encryption WEP TKIP (RC4) CCMP (AESCounter Mode)
Integrity None Michael MIC CCMP (AESCBC-MAC)
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Tools and Techniques
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Hacker Tools and Techniques
Discovery
Association Polling Set SSID to Any on Client Card automatically associates with the strongest AP Default setting for most wireless clients
* Reason that Fake APs are a threat to unsuspecting clients
Scan Mode Polling Send a Scan Request to the card, receive a Scan response back with AP info Card keeps track of received beacon packets and probe requests Will detect both APs as well as adhoc networks Will only detects Access Points that are configured to Beacon the SSID Technique used by Netstumbler
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Hacker Tools and Techniques
Discovery Tools
Kismet Runs on Linux Cards must be capable of running in RF-Monitor Mode Can also be setup with drones to use it as a wireless intrusion
detection solution.
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Summary Best Practices
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