1. Quickest Detection of GPS Spoofing Attack Z. Zhang, M. Trinkle, L. Qian, and H. Li MILCOM 2012 Nadia Adem 10/27/2014

2. Global Positioning System

3. GPS spoofing attacks

4. GPS Spoofing

5. Detecting GPS Spoofer

6. Outline  Contributions  Anti-spoofing system  Experiment setup  Problem formulation  Detection techniques  Performance evaluation  Summary

7. Contributions  Simple hardware installation  Probabilistic-based detection

8. Anti-spoofing System

10. Experiment Setup Photo of the lab. and devices Lab. setup diagram

11. Probabilistic Detection  Samples of signal to noise power ratios - the two antennas  Distribution of standard deviation of the difference

12. Experiment Result Estimated PDF

13. Problem Formulation and Constraints  Minimize worst case delay  False alarm below a certain threshold

14. Hypothesis Testing  Let the signal be y(t), model be h(t) Hypothesis testing: H0: y(t) = n(t) (no signal) H1: y(t) = h(t) + n(t) (signal)  The optimal decision is given by the Likelihood ratio test (Nieman-Pearson Theorem), g is a threshold. Select H1 if L(y) = log(P(y|H1)/P(y|H0)) > g; otherwise select H0.

15. Signal detection paradigm

16. Receiver operating characteristic (ROC) curve Tradeoff between false alarm and detection probability

17. Cusum test (Page, 1966) gngn b Stopping time N This test minimizes the worst-average detection delay (in an asymptotic sense)

18. Performance Evaluation

20. My Comments  Probabilistic knowledge about attacker  Space Diversity

21. Summary  GPS spoofing threat  Proposed anti-sp0oing system  Detection schemes  Effectiveness of the proposed schem