Melvyn Kwek figured out something was wrong when US federal agents began to visit him in 2022. “Could you take a look at your network?” they asked Kwek, who’d been running cybersecurity at the Guam Power Authority, an autonomous agency of the island’s government, for the previous six years. And then, more furtively, “Could we take a look at your network?”Looking at a network, in this case, meant analyzing the vast amount of data traffic flowing through its routers and switches—often for months a...