WASHINGTON (AP) — A Chinese cyberespionage group called APT10 relentlessly attacks U.S. engineering, telecom and aerospace industries. Russian hackers last year compromised dozens of U.S. energy companies. Iranian hackers known as "Rocket Kitten" repeatedly target American defense companies in hopes of stealing information to boost Tehran's missile and space programs.

While Moscow's efforts to meddle in the 2016 U.S. presidential election are widely known, spy services from China, Russia and Iran, along with their proxy hackers, also are hard at work trying to steal trade secrets and proprieta...