Microsoft president calls SolarWinds hack an "act of recklessness"

SolarWinds is the maker of a nearly ubiquitous network management tool called Orion. A surprisingly large percentage of the world's enterprise networks run it. Hackers backed by a nation-state--two US senators who received private briefings say it was Russia--managed to take over SolarWinds' software build system and push a security update infused with a backdoor. SolarWinds said about 18,000 users downloaded the malicious update.

"A software build system" is the code and procedures to turn the code into a functioning program.  

How they managed to penetrate and subvert the build system is, AFAIK, unknown.  

She believed in nothing; only her skepticism kept her from being an atheist. -- Jean-Paul Sartre