Why vessels passing near Iran may have trouble staying on course

THE STRAIT OF HORMUZGNSSGPSFBI is hard to navigate at the best of times. It is narrow, crooked, dotted with islands and, as the only way in or out of the Persian Gulf, busy. Recently, a new peril has joined the list: that satellite-navigation systems may be “spoofed” to lure vessels off course.The world has four global-navigation satellite systems (), of which is the best known. Global shipping—and much else—is almost completely reliant on them. But in 2008 an American academic named Todd Humphreys revealed that satnav systems could be fooled by sending counterfeit signals. Five years later he proved it by sending a big yacht miles out of its way, to the consternation of the . An Iranian general once boasted of his forces’ prowess in this technique, which appears to have been used in 2011 to inveigle an American drone from Afghan airspace into Iran, where it was captured and put on display.