More than 20,000 U.S. organizations have been compromised through a back door installed via recently patched flaws in Microsoft Corp.'s email software, a person familiar with the U.S. government's response said Friday.
The hacking has already reached more places than all of the tainted code downloaded from SolarWinds Corp., the company at the heart of another massive hacking spree uncovered in December.
The latest hack has left channels for remote access spread among credit unions, town governments and small businesses, according to records from the U.S. investigation.