Salt Typhoon is behind one of the broadest hacking campaigns in recent years, targeting some of the world’s largest phone and internet companies and stealing tens of millions of phone records about senior government officials. The hacking group, attributed to China, is part of a wider cluster of hackers with the collective aim of helping China prepare for an eventual war with Taiwan, according to researchers. U.S. officials have called China’s potential invasion of Taiwan an “epoch-defining threat.” Much of the group’s efforts have focused on hacking Cisco routers at the edge of a company’s network to break in, and taking control of surveillance devices that U.S. telecom companies are legally required to install to allow law enforcement to monitor calls and messages.…