The discovery of the malware has raised fears that Chinese hackers, probably working for the People's Liberation Army, have inserted code designed to disrupt U.S. military operations in the event of a conflict, including if Beijing moves against Taiwan in coming years.

The malware, one congressional official said, was essentially "a ticking time bomb" that could give China the power to interrupt or slow American military deployments or resupply operations by cutting off power, water and communications to U.S. military bases. But its impact could be far broader, because that same infrastructure often supplies the houses and businesses of ordinary Americans, according to U.S. officials.

The first public hints of the malware campaign began to emerge in late May, when Microsoft said it had detected mysterious computer code in telecommunications systems in Guam, the Pacific island with a vast American air base, and elsewhere in the United States.

More than a dozen U.S. officials and industry experts said in interviews over the past two months that the Chinese effort predated the May report by at least a year, and that the U.S. government's effort to hunt down the code, and eradicate it, has been underway for some time. Most spoke on the condition of anonymity to discuss confidential and in some cases classified assessments.