The cyberattack that shut down the Colonial Pipeline that delivers gas and jet fuel to the East Coast has sparked new fears among experts of a broader Russian-backed assault that could darken the U.S. electric grid in just 24 hours.

Using easy-to-build electronic weapons installed in just 20 little trucks, enough attacks on little-guarded grid transformers over 24 hours could turn the United States into a cave society, according to a leading electronic and cyber weapon expert.