Hackers Won’t Let Up in Their Attack on U.S. Cities

BALTIMORE—Local governments across the country are facing a growing threat of cyberattacks and escalating ransom demands, as an attack in this city has crippled thousands of computers for a month.

“Ransomware is a pandemic in the United States,” said Joel DeCapua, supervisory special agent in the Federal Bureau of Investigation’s cyber division, referring to a particularly devastating form of malicious software.