The lead U.S. agency for protecting the electric grid, water supply and other critical services from hacking has furloughed most of its already trimmed-down staff in the government shutdown, just as a decade-old law giving companies leeway to collaborate on cyberdefense expired.The twin impacts leave employees at the Cybersecurity and Infrastructure Security Agency and outside professionals unsettled as they try to fend off a surge in sophisticated hacks from China as well as continued ransomwar...