1. WLAN 보안

2. Requirements for Secure Wireless LANs
WLAN Security
Requirements for Secure Wireless LANs
Authentication
Access Control
Data Privacy
Data Integrity
Protection Against Replay

3. WLAN Attack Wardriving 워드라이빙 :
Driving around looking for unsecured wireless networks.
term coined by Pete Shipley
워드라이빙 :
이동수단을 이용하여, 무인증 무선네트워크를 찾아다니는 행위
해킹 경유지의 순차적 추적 불가능
무선 AP에는 접속 로그 미존재
실시간 추적시에도 무선 AP로부터 접속자 위치 확인 불가능
실시간 이동 공격자에 대한 추적 대책 미흡
(핸드폰 위치추적기술과 같은 방법 개발 필요)

4. MAC address Authentication Attack
Strengths (장점)
MAC 주소를 기반으로 AP에 접속하고자 하는 Station들을 제어
Weaknesses (단점)
MAC 주소는 쉽게 위조 가능
무선랜 네트워크를 모니터링(sniffing)함으로써 쉽게 MAC 주소를 획득
공격자들은 무선랜 통신을 계속 감시 가능
MAC 주소의 Brute-force 공격이 가능
Man in the middle attack 기술로 네트워크가 공격에 노출
TOOL
Windows
AiroPeek : Wireless Network Management Tool
SMAC : MAC address Changer
- Linux
Kismet : Wireless Network Sniffing Tool
macchanger : MAC address Changer

5. MAC Address Attack

6. Rogue AP – Spoofing Attack
Station은 항상 가장 신호가 센 AP로 접속
Attacker는 목표 AP와 동일한 SSID를 사용
Attacker는 목표 AP보다 강한 신호를 발생시켜
Victim이 접속하기 가장 용이한 AP로 위장
Victim은 아무런 의심없이 AP에 접속
Attacker는 정상적인 홈페이지를 위장한 가상홈페이지를 열어놓고 ID와 PW 입력 유도

7. Rogue AP – Spoofing Attack

8. Attacker Passive Monitoring
Access Point
Username: dziminski
Password:cleartext
Station
Attacker Passive Monitoring
Captures data

9. 802.11 DOS Attack X Access Point Connection is broken Station
Attacker spoofs
Disassociate frame

10. 802.11 Man in the Middle Attack
Attacker broadcasts spoofed AP SSID and MAC Address
Station unknowingly connects to attacker
MIM attacks can always be established
But if strong authentication and encryption are used, attacker will be nothing more than a bridge.
Station
Access Point
Station MAC Address
Attacker
AP MAC Address
Station MAC Address
AP MAC Address

11. Authentication and Encryption Standards
Credentials
Certificate
Username/Password
TLS
PEAP
Authentication Protocols
EAP
802.1x
Encryption Algorithms
RC4
RC4
AES
Encryption Standards
WEP
WPA-TKIP
802.11i
WEP: Wired Equivalent Privacy , WPA: Wi-Fi Protected Access, TKIP: Temporal Key Integrity Protocol
PEAP: Protected Extensible Authentication Protocol; uses server-side public key certificates to authenticate the server

12. Evolution of WLAN Security
WEP: not adequate
IEEE formed a Task Group “i” to develop i standard
Objective: to produce a detailed specification to enhance the security features for WLANs
IEEE 802
Working group
IEEE
WLAN WG
IEEE i
WLAN security
RSN
TSN
Robust
Security Network
Transitional
Security Network

13. Evolution of WLAN Security
Responses from Wi-Fi Alliance
The industry cannot wait for the i standard. It is demanding a more secure wireless environment right now
Wi-Fi Alliance, together with IEEE, developed Wi-Fi Protected Access (WPA) to offer a strong interoperable security standard to the market
802.11i contributed TKIP (encryption) and MIC (integrity) algorithms, which were being developed for RSN but applicable to WPA
Wi-Fi Alliance
IEEE i
WPA
TKIP +
MIC
Temporal Key
Integrity Protocol
Message
Integrity Check
Wi-Fi Protected Access

14. High-level Differences Between RSN and WPA
Designed from the start, without regards to existing WEP systems
Will require new hardware to support new methods of encryption
Supports options for encryption (privacy)
TKIP
AES
WPA
Designed with constraints around existing WEP systems
Objective: use same hardware and upgrade software only
Only supports one encryption standard: TKIP
Essentially, the two approaches are very similar and built around the same security architecture

15. Encrypted with 40 or 104 bit key. RC4 Algorithm.
WEP Encryption
24 bit IV clear text
integrity check IV
Payload
CRC-32
Encrypted with 40 or 104 bit key. RC4 Algorithm.
WEP has several problems
IV is too small. At 10,000 packets per second IV repeats in 0.5 hours.
- For 24 bits, an IV will be reused after packets if IV
value is incremented by 1 each time. For a device sending 10,000 packets per second
24-bit IV takes half an hour to rollover
There are several “weak keys”. Those are especially vulnerable.
No key update mechanism built in.
Message replay attacks. DOS. 15

16. WPA Key features to address WEP vulnerabilities
Access Control and Authentication:
Implements 802.1X EAP based authentication to enforce mutual authentication
Encryption
Applies Temporal Key Integrity Protocol (TKIP) on existing WEP to impose strong data encryption
Integrity
Uses Message Integrity Check (MIC) rather than CRC-32 for message integrity
WPA also presents some potential security issues
There are still potential encryption weaknesses in TKIP. Fortunately, the successful crack is expected to be heavy and expensive.
Performance may be sacrificed potentially due to a more complex and computation intensive authentication and encryption protocols.
Note: The ultimate wireless security solution is still i RSN. All products are supposed to comply with RSN standard since it is released, often under the name WPA2.

17. Wi-Fi Protected Access (WPA) TKIP-Encryption
Wi-Fi Protected Access is an interim standard created by the Wi-Fi alliance (group of manufacturers).
WPA-TKIP fixes problems with WEP.
IV changes to 48 bits with no weak keys years to repeat an IV
at 10k packets/sec
Use IV as a replay counter
Message integrity
Per-packet keying
Supported on many wireless card and on Windows XP (after applying 2 hot fixes).
Uses 802.1x for key distribution.
Can also use static keys. 17

18. Key features to address WEP vulnerabilities
802.11i RSN
Key features to address WEP vulnerabilities
Access Control and Authentication
Implements 802.1X EAP based authentication to enforce mutual authentication (same as WPA)
WRAP: RSN includes a Wireless Robust Authentication Protocol. Uses AES in offset codebook mode (OCB) for encryption and integrity.
Encryption
TKIP: In order to support legacy device, the i chooses TKIP as one of the encryption options
AES: Stands for Advanced Encryption Standard, which is a much stronger encryption algorithm. AES requires a hardware coprocessor to operate
Integrity
Uses Michael Message Integrity Check (MIC) for message integrity
Other security features: Secure IBSS (Ad Hoc mode), secure fast handoff, secure de-authentication and disassociation.
Supports Roaming
Is referred to as WPA2 by the Wi-Fi Alliance
IBSS: Independent Basic Service Set

19. 802.11i AES-encryption Ratified by the IETF in June of 04.
Uses the AES algorithm for encryption and 802.1x for key
distribution.
Backwards compatible with TKIP to support WPA clients.
802.11i not in many products yet. 19

20. Access Control and Authentication – 802.1X / EAP
Initially designed for wired networks but is now applicable to WLANs.
Provides port-based access control and mutual authentication between client and APs via an authentication server.
802.1X standard is comprised of three elements
A supplicant: the client (laptop, PDA,…) who wants to be authenticated
An authenticator: the AP, which acts as an intermediary between a supplicant and an authentication server.
An authentication server: such as a RADIUS (Remote Access Dial-In User Service) server.
Access Point
Authenticator
Station
Supplicant
RADIUS Server
Authorizer

21. Access Control and Authentication – 802.1X / EAP
EAP (Extensible Authentication Protocol): protocol that 802.1X uses to manage mutual authentication.
Initially developed for use with PPP (RFC2284)
Several EAP types depending on the authentication method (passwords, PKI certificates,…)
EAP-MD5
EAP-TLS
EAP-TTLS
PEAP
LEAP
EAP-SIM
The authenticator does not need to understand the details about authentication methods. It simply package and repackage EAP packets, usually between Supplicant and RADIUS

22. 802.1x EAP-TLS Authentication
Client digital cert
From XYZ CA
Access Point
Authenticator
Station
Supplicant
RADIUS Server
Authorizer
Server Digital cert
From XYZ CA

23. 802.1x PEAP authentication Phase 1: Authenticate AP. Secure tunnel
to AP using TLS
Digital cert
From XYZ CA
Access Point
Authenticator
Station
Supplicant
RADIUS Server
Authorizer
Username Dan
Password: encrypted
Phase 2:
Password authentication
with directory server
Success/Fail
Directory Server

24. LEAP (Lightweight Extensible Authentication Protocol)
LEAP Characteristics
Primarily developed by Cisco for Aironet WLAN deployments.
Cisco is now licensing the software, other vendors are now beginning to support LEAP in their wireless LAN adapters.
Encrypts data transmissions using dynamically generated WEP keys and supports mutual authentication.
No certificates are required
Uses bi-directional challenge-response with user password as shared secret
Transaction sent in clear text (dictionary attacks !)

25. EAP Authentication Types Comparison Chart
802.1x EAP Types Feature / Benefit
MD5
TLS
TTLS
PEAP
LEAP
Client side certificate required no
yes
Server side certificate required
WEP key management
Rogue AP detection
Developer
Authentication Attributes
One way
Mutual
Deployment
Easy
Difficult
Moderate
Wireless Security
Poorest
Highest
High