Malicious hackers, often under the protection of hostile foreign states, have engaged in massive data theft from U.S. business firms and private institutions. Intelligence agencies predict the problem will get worse. There have been numerous calls for U.S. retaliation – “hacking back.” Many commentators worry that hack-back will spur international tensions and hurt innocent bystanders. We think the worries are misplaced. We advocate letting private cyber security firms use hack-back methods to track down cyber predators. A new administration could provide legal protection for such measures without changing existing law.