MIAMI — The U.S. Department of Justice has disrupted a major ransomware group — and enabled some people to restore their systems — with South Florida playing a central role in the cybercrime investigation, authorities said. The FBI this month seized several websites operated by the Blackcat ransomware group, launched a disruption campaign, and “gained visibility” into the group’s computer network, according to an affidavit supporting a search warrant unsealed Tuesday in the Southern District of Florida. The FBI developed a decryption tool that allowed its field offices nationwide and internati…