Now, its banking system is being hit by a new wave of attacks On a Tuesday morning in early January, the computer system at Mexico’s state-owned trade bank went haywire. Some of Bancomext’s workers couldn’t get their PCs to turn on. The internet was slow. Routine operations were taking longer than normal. Inside the lender’s concrete-and-glass building on the southern outskirts of Mexico City, a mid-level technician was monitoring messages coming in on the Swift network, the air-traffic...