More than 20,000 U.S. organizations compromised through Microsoft flaw - source

FILE PHOTO: A Microsoft logo is seen on an office building in New York City on July 28, 2015. REUTERS/Mike Segar/File Photo/File Photo

WASHINGTON (Reuters) - 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 on 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.