  Consider the problem of mitigating the impact on data integrity of phasor
measurement units (PMUs) given a GPS spoofing attack. We present a sparse error
correction framework to treat PMU measurements that are potentially corrupted
due to a GPS spoofing attack. We exploit the sparse nature of a GPS spoofing
attack, which is that only a small fraction of PMUs are affected by the attack.
We first present attack identifiability conditions (in terms of network
topology, PMU locations, and the number of spoofed PMUs) under which data
manipulation by the spoofing attack is identifiable. The identifiability
conditions have important implications on how the locations of PMUs affect
their resilience to GPS spoofing attacks. To effectively correct spoofed PMU
data, we present a sparse error correction approach wherein computation tasks
are decomposed into smaller zones to ensure scalability. We present
experimental results obtained from numerical simulations with the IEEE RTS-96
and IEEE 300 test networks to demonstrate the effectiveness of the proposed
approach.
