It spurred extensive controversy last year when Charter Communications, one of the country’s largest ISPs, announced that it planned to use deep-packet inspection to spy on broadband customers to help advertisers deliver targeted ads. The plan sparked a backlash and heated congressional hearings. Publicity about the issue died down, however, after Charter retreated from its plan, and Congress moved on to other matters. But deep-packet inspection didn’t go away. ISPs insist they need it to help combat spam and malware. But the technology is ripe for abuse, not only by ISPs but also by the U.S. government, which could force providers to retain and hand over data they collect about users.