Two seperate incidents shows just how powerful cyber weapons can be.
Tech Republic explains:
At 11:42 pm, Britt's eyes snapped open. She shot up in bed, wide awake, heart pounding. Sirens screamed. Her neighbors hollered and scrambled around the courtyard of her modern Dallas apartment complex. The Midwest native is accustomed to hearing storm sirens. The Dallas sirens were different. And louder. The blaring monotone warning radiated from every direction.
"In a tornado, the siren will shut off when the storm passes. These were much louder and blasted for a long time. We had no idea what was going on, but we knew it wasn't a tornado. There was a guy standing close to my window screaming, 'We're at war! The shit's going down!'" For a fleeting moment, she said, "I thought he might be right."
On April 7, 2017, a radio frequency trigger hack caused 156 emergency sirens in Dallas, a city of 1.2 million people, to wail concurrently for 81 minutes. The incident serves as a clarion call to organizations everywhere that cyberweapons could be used against your infrastructure in order to make a statement.
"Technically, each siren went off for 90 seconds, 15 times. There was a lot of confusion," said Dallas public information officer Richard Hill, because there were no storms in the region. "We had close to 4,000 calls to 911. The system was nearly overwhelmed."