  The COVID-19 pandemic has impacted our society by forcing shutdowns and
shifting the way people interacted worldwide. In relation to the impacts on the
electric grid, it created a significant decrease in energy demands across the
globe. Recent studies have shown that the low demand conditions caused by
COVID-19 lockdowns combined with large renewable generation have resulted in
extremely low-inertia grid conditions. In this work, we examine how an attacker
could exploit these {scenarios} to cause unsafe grid operating conditions by
executing load-altering attacks (LAAs) targeted at compromising hundreds of
thousands of IoT-connected high-wattage loads in low-inertia power systems. Our
study focuses on analyzing the impact of the COVID-19 mitigation measures on
U.S. regional transmission operators (RTOs), formulating a plausible and
realistic least-effort LAA targeted at transmission systems with low-inertia
conditions, and evaluating the probability of these large-scale LAAs.
Theoretical and simulation results are presented based on the WSCC 9-bus {and
IEEE 118-bus} test systems. Results demonstrate how adversaries could provoke
major frequency disturbances by targeting vulnerable load buses in low-inertia
systems and offer insights into how the temporal fluctuations of renewable
energy sources, considering generation scheduling, impact the grid's
vulnerability to LAAs.
