A hacker set off all 156 of Dallas's emergency sirens Friday night.
"It does appear at this time it was a hack, and it does appear this came from the Dallas area," Sana Syed, the city's managing director of public information, said at a Saturday news conference.
The alarms sounded at about 11:40 p.m. and were turned off by 1:20 a.m. Saturday, but not before officials had to shut down Dallas's emergency system.
The FBI sought to assure residents - thousands of whom called 911 - by tweeting that the emergency sirens were malfunctioning and noting there was no bad weather or active emergency afoot. Authorities are investigating.
“As we continue to connect more of the devices and facilities that simplify, enhance and protect our lives to the global communications network, we increase the risk that cyber attackers will disrupt our lives. Compromising an emergency siren may seem like mischief, but these sorts of attacks can also erode the public's trust in emergency services," Carbon Black National Security Strategist Eric O'Neill, a former FBI agent, said in emailed comments to SC Media. "If normal operations are disrupted by cyber attackers, then when a true emergency occurs, the public may ignore the warnings. Attacks against our critical infrastructure no longer require physical access or kinetic explosives. In a time when everything is connected, everything can be compromised.”