(Reuters) - The FBI is investigating a mysterious postcard sent to the home of cybersecurity firm FireEye's chief executive days after it found initial evidence of a suspected Russian hacking operation on dozens of U.S. government agencies and private American companies.
U.S. officials familiar with the postcard are investigating whether it was sent by people associated with a Russian intelligence service due its timing and content, which suggests internal knowledge of last year's hack well before it was publicly disclosed in December.