Thousands of ships navigate northern Europe's Baltic Sea each day. Among the world's busiest shipping routes, this vast arm of the Atlantic Ocean has connected the region to global trade for centuries. In recent years, however, what lies beneath the sea's surface has been more important to governments than what sails above: the myriad of subsea internet cables which power their modern economies. Last month, to the alarm of governments in close-by Latvia and Sweden, one of those cables mysteriously malfunctioned in what appeared to be an act of sabotage. It left top engineers scrambling to squash the threat of…