"It's unfortunate that it has taken over three weeks after the revelation of an intrusion this significant for this Administration to finally issue a tentative attribution," said Senator Mark Warner, vice chairman of the Senate Intelligence committee.
Source code - the underlying set of instructions that run a piece of software or operating system - is typically among a technology company’s most closely guarded secrets and Microsoft has historically been particularly careful about protecting it.
Because the attackers could use SolarWinds to get inside a network and then create a new backdoor, merely disconnecting the network management program is not enough to boot the hackers out, experts said.