WASHINGTON (Reuters) - - An unidentified hacking group launched a massive cyberattack on a telecommunications company in the U.S. heartland late last year that disabled hundreds of thousands of internet routers, according to research published Thursday. Security analysts with Lumen Technologies' Black Lotus Labs discovered the attack in recent months and reported on it in a blog post. The October incident, which was not disclosed at the time, took more than 600,000 internet routers offline.