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

Global Positioning System

GPS spoofing attacks

GPS Spoofing

Detecting GPS Spoofer

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

Contributions  Simple hardware installation  Probabilistic-based detection

Anti-spoofing System

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

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

Experiment Result Estimated PDF

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

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.

Signal detection paradigm

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

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

Performance Evaluation

My Comments  Probabilistic knowledge about attacker  Space Diversity

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