U.S. officials are urging telecommunication companies to boost network security following a Chinese hacking operation that gave officials in Beijing access to the private texts and phone conversations of Americans. The warning issued Tuesday by the FBI and the Cybersecurity and Infrastructure Security Agency includes technical recommendations designed to prevent similar incursions in the future. Officials say the hackers retrieved calls and texts from a small number of victims, many of whom work in government or politics, and obtained the metadata from a much larger number of victims. The FBI has notified people in the first group and says it is investigating how far the intrusion went.