Bret Padres, a former Air Force computer-crime investigator who is now the C.E.O. of the Crypsis Group, a cyberforensics firm, told me about some work he had done for a defense contractor whose server had been breached. He examined malicious code that the hackers had left behind, and found that it contained the I.P. address of the hackers’ hop point, along with their sign-in credentials. Soon after Padres shared this information with the client, a member of the company’s I.T. team hacked into the hop point and grabbed all the data. How did the contractor’s lawyers justify the raid? “They weren’t asked,” Padres said.