SolarWinds software was used to hack the U.S. Treasury Department and Department of Commerce. Hackers apparently added malicious code to SolarWinds Orion, a program used by computer network administrators. Once installed, the program connected to a server controlled by the hackers and allowed them to steal data from SolarWinds customers. The Wall Street Journal was told this by Microsoft, which analyzed the incident. SolarWinds' customer list includes more than 400 of the largest U.S. Fortune 500 companies and many government agencies.