Two cargo vessels making their way toward American shores have been seized not by pirates of the old world, but by the invisible hands of cyberattack — a reminder that the ancient arteries of global trade now pulse with digital vulnerabilities as much as saltwater. US officials, disclosing the breach this week, have cast a light on a long-shadowed truth: that the ships carrying the sinew of modern commerce are, in many ways, among the least defended nodes in the nation's critical infrastructure. The sea has always carried risk, but the nature of that risk has quietly transformed.