Phasor Measurement Units (PMUs) provide real-time control, situational awareness and early fault identification for transmission and distribution grids. Because PMUs are typically deployed to large geographic areas, a common and trusted time source is necessary to synchronize and guarantee their performance. GPS technology is currently used to provide this common time; however, due to the nature of GPS signals (unencrypted low-power radio frequency), an attacker could jam or spoof GPS, resulting in potential grid destabilization. This session describes a novel approach based on NI CompactRIO FPGA technology for detection and mitigation of known GPS attacks applied to PMUs.