“This is only the beginning of a new era of cyber-warfare,” warned Handala, an Iranian hacker group, after breaching Stryker, an American medical company, earlier this month. The attack, according to the group, wiped data on more than 200,000 servers and devices. Much of the firm’s operations were disrupted. Iran has a long track record of launching cyber-attacks on American interests in response to real-life skirmishes in the Middle East. Such operations offer a way to bring the war in the Gulf...