Washington, Feb. 2 -- U.S. officials said Wednesday they disrupted a state-backed Chinese effort to plant malware that could be used to damage civilian infrastructure, as the head of the FBI warned that Beijing is positioning itself to disrupt the daily lives of Americans if the United States and China ever go to war.

The operation, announced just before FBI Director Chris Wray addressed House lawmakers, disrupted a botnet of hundreds of U.S.-based small office and home routers owned by private citizens and companies that had been hijacked by the Chinese hackers to cover their tracks as they sowed the malware. Their ultimate targets included water treatment plants, the electrical grid and transportation systems across the United States....