Here is more from 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.
A disinformation researcher from the Rand Corporation, Todd Helmus, received a similar postcard in 2019, based on an image of it Helmus posted to Twitter. Helmus, who studies digital propaganda, said he received the postcard after testifying to Congress about Russian disinformation tactics.
Dr. Todd Helmus is a Senior Behavioral Scientist at the RAND Corporation and a member of the Pardee RAND Graduate School faculty.
Here is a picture of the postcard that Dr. Helmus received.