Yan Chen, Hai ZhouNorthwestern Lab for Internet

and Security Technology (LIST)

Dept. of Electrical Engineering and Computer Science

Northwestern University

http://list.cs.northwestern.edu

Vulnerability Analysis and Intrusion Mitigation Systems for WiMAX

Networks Motorola Liaisons

Greg W. Cox, Z. Judy Fu, Peter McCann, and Philip

R. Roberts

Motorola Labs

The Current Threat Landscape and Countermeasures of WiMAX

Networks • WiMAX: next wireless phenomenon

– Predicted multi-billion dollar industry

• WiMAX faces both Internet attacks and wireless network attacks– E.g., 6 new viruses, including Cabir and Skulls, with

30 variants targeting mobile devices

• Goal of this project: secure WiMAX networks• Big security risks for WiMAX networks

– No formal analysis about WiMAX security vulnerabilities

– No intrusion detection/mitigation product/research tailored towards WiMAX networks

Our Approach

• Vulnerability analysis of 802.16e specs and WiMAX standards– Intelligent and complete checking through combo of

manual analysis + auto search through formal methods

– First, manual analysis provide hints and right level of abstraction for auto search

– Then specify the specs and potential capabilities of attackers in a formal language TLA+ (the Temporal Logic of Actions)

– Then model check for any possible attacks

• Adaptive Intrusion Detection and Mitigation for WiMAX Networks (WAIDM) – Could be differentiator for Motorola’s 802.16 products

Outline• Threat landscape and motivation• Our approach• Accomplishment of this year• Achievement highlight: a Mobile IPv6

vulnerability• Plan for the next year

Accomplishments This Year (I)• Most achieved with close interaction with

Motorola liaisons• Intelligent vulnerability analysis of WiMAX

– Focused on outsider attacks, i.e., w/ unprotected msgs

– Checked the complete spec of 802.16e before authentication

» Found some vulnerability, e.g., for ranging (but needs to change MAC)

» Published a joint paper with Motorola Labs

“Automatic Vulnerability Checking of IEEE 802.16 WiMAX Protocols through TLA+”, in Proc. of the Second Workshop on Secure Network Protocols (NPSec), 2006.

– Checked the mobile IPv4/v6» Find an easy attack to disable the route optimization of

MIPv6 !

Accomplishments This Year (II)• Automatic polymorphic worm signature

generation systems for high-speed networks– Fast, noise tolerant w/ proved attack resilience– Resulted a joint paper submission with Motorola Labs

“Network-based and Attack-resilient Length Signature Generation for Zero-day Polymorphic Worms”, submitted to IEEE International Conference on Network Protocols (ICNP) 2007.

– Patent under review by the patent committee of Motorola

Automatic Length Based Worm Signature Generation

• Majority of worms exploit buffer overflow vulnerabilities

• Worm packets have a particular field longer than normal

• Length signature generation– Parse the traffic to different fields– Find abnormally long field– Apply a three-step algorithm to determine a

length signature– Length based signature is hard to evade if the

attacker has to overflow the buffer.

Length Based Signature Generator

Filter

SuspiciousTraffic Pool

NormalTraffic Pool

YESQuit

SignaturesLESGCore

ProtocolSpecification

ParsedNormal

ParsedSuspicious

ProtocolParser

NO

Pool sizetoo small?

Evaluation of Signature Quality

• Seven polymorphic worms based on real-world vulnerabilities and exploits from securityfocus.com

• Real traffic collected at two gigabit links of a campus edge routers in 2006 (40GB for evaluation)

• Another 123GB SPAM dataset

Accomplishments on Publications

• Four conference papers and one tech report– “Detecting Stealthy Spreaders Using Online

Outdegree Histograms”, in the Proc. of the 15th IEEE International Workshop on Quality of Service (IWQoS), 2007 (26.6%).

– “A Suite of Schemes for User-level Network Diagnosis without Infrastructure”, in the Proc. of IEEE INFOCOM, 2007 (18%).

– “Towards Scalable and Robust Distributed Intrusion Alert Fusion with Good Load Balancing”, in Proc. of ACM SIGCOMM Workshop on Large-Scale Attack Defense 2006(33%).

– Automatic Vulnerability Checking of IEEE 802.16 WiMAX Protocols through TLA+, in Proc. of the Second Workshop on Secure Network Protocols (NPSec) (33%).

– Abstraction Techniques for Model-Checking Parameterized Systems, EECS Tech. Report, 2007.

Students Involved

• PhD students: – Zhichun Li, Yao Zhao (all in their 3rd years)– Lanjia Wang, Yanmei Zhang (visiting PhD

students)– Nicos Liveris (4th year)

• MS students: – Prasad Narayana (graduated) – Sagar Vemuri (1st year)

Outline• Threat Landscape and Motivation• Our approach• Accomplishment• Achievement highlight: a Mobile IPv6

vulnerability• Plan for the next year

Mobile IPv6 (RFC 3775)

• Provides mobility at IP Layer

• Enables IP-based communication to continue even when the host moves from one network to another

• Host movement is completely transparent to Layer 4 and above

Mobile IPv6 - Entities

• Mobile Node (MN) – Any IP host which is mobile

• Correspondent Node (CN) – Any IP host communicating with the MN

• Home Agent (HA) – A host/router in the Home network which:– Is always aware of MN’s current location– Forwards any packet destined to MN– Assists MN to optimize its route to CN

Mobile IPv6 - Process

• (Initially) MN is in home network and connected to CN

• MN moves to a foreign network:– Registers new address with HA by sending Binding

Update (BU) and receiving Binding Ack (BA)– Performs Return Routability to optimize route to CN

by sending HoTI, CoTI and receiving HoT, CoT– Registers with CN using BU and BA

Mobile IPv6 in Action

Home AgentCorrespondent

Node

Home Network

Foreign Network

InternetMobile Node

Mobile Node

HA

– MN

TunnelBU

BAHoTI

HoTI

CoTI

HoT

HoT

CoT

BU

BA

Mobile IPv6 Vulnerability

• Nullifies the effect of Return Routability• BA with status codes 136, 137 and 138

unprotected• Man-in-the-middle attack

– Sniffs BU to CN– Injects BA to MN with one of status codes above

• MN either retries RR or gives up route optimization and goes through HA

MIPv6 Attack In ActionMN HA AT CN

HoTI

HoTI

CoTI

CoT

HoTHoT

Start Return

Routability

Restart Return

Routability

Silently Discard

Bind Ack

Bind Update (Sniffed by AT along the way)

Bind Ack Spoofed by AT

Bind Ack

• Only need a wireless network sniffer and a spoofed wired machine (No MAC needs to be changed !)

• Bind ACK often skipped by CN

MIPv6 Vulnerability - Effects

• Performance degradation by forcing communication through sub-optimal routes

• Possible overloading of HA and Home Link• DoS attack, when MN repeatedly tried to

complete the return routability procedure • Attack can be launched to a large number of

machines in their foreign network– Small overhead for continuously sending spoofed

Bind ACK to different machines

TLA Analysis and Experiments

• With the spec modeled in TLA, the TLC search gives two other similar attacks w/ the same vulnerability– Complete the search of vulnerabilities w/

unprotected messages

• Implemented and tested in our lab– Using Mobile IPv6 Implementation for Linux (MIPL)– Tunnel IPv6 through IPv4 with Generic Routing

Encapsulation (GRE) by Cisco– When attack in action, MN repeatedly tried to

complete the return routability procedure – DOS attack !

Outline• Threat landscape and motivation• Our approach• Accomplishment• Achievement highlight: a Mobile IPv6

vulnerability• Plan for the next year

– Vulnerability analysis of EAP protocols– Insider attack analysis– Technology transfer

Extensible Authentication Protocols (EAP)

PPP802.3

Ethernet

802.5

Token Ring

802.11

WLAN802.16

EAP-FASTEAP-TTLS EAP-SIM EAP-AKAEAP-TLS

EAP Over LAN (EAPOL)

Extensible Authentication Protocol (EAP)

EAP Layer

Data Link Layer

Authentication method layer

GSM CDMA

PEAP

Extensible Authentication Protocols (EAP)

• EAP is an authenticaiton framework– Support about 40 different EAP methods

• Current targets– EAP-SIM for GSM cellular networks– EAP-AKA for 3G networks, such as UMTS and

CDMA2000– EAP-FAST (Flexible Authentication via Secure

Tunneling)»Most Comprehensive and secure EAP method

for WLAN»Will compare it w/ EAP-SIM and EAP-AKA

Insider Attack Analysis • Not hard to become a subscriber• Can five subscribers bring down an entire

WiMAX network ?• Check vulnerability after authentication

• Plan to analyze various layers of WiMAX networks– IEEE 802.16e: MAC layer– Mobile IP v4/6: network layer– EAP layer

802.16e SS Init Flowchart

Work Done

Future work

Conclusions

• Vulnerability analysis of WiMAX protocols: 802.16e and mobile IP specs

• Adaptive Intrusion Detection and Mitigation for WiMAX Networks (WAIDM)

Thank You !

Existing WLAN Security Technology Insufficient for

WiMAX Networks • Cryptography and authentication cannot prevent

attacks from penetrating WiMAX networks– Viruses, worms, DoS attacks, etc.

• 802.16 IDS development can potentially lead to critical gain in market share– All major WLAN vendors integrated IDS into products

• Limitations of existing IDSes (including WIDS)– Mostly host-based, and not scalable to high-speed

networks– Mostly simple signature based, cannot deal with

unknown attacks, polymorphic worms– Mostly ignore dynamics and mobility of wireless

networks

Deployment of WAIDM

• Attached to a switch connecting BS as a black box• Enable the early detection and mitigation of global

scale attacks• Could be differentiator for Motorola’s 802.16 products

Original configuration WAIDM deployed

Internet

802.16BS

Users

(a)

(b)

802.16BS

Users

Switch/BS controller

Internet

sca

n

po

rtW

AID

Msy

ste

m

802.16BS

Users

802.16BS

Users

Switch/BS controller