Largest impact, sure. But architecturally it was a relatively simple formula - compromise a widely used package and sleep on it until it was pervasive enough to be a valuable hack. I disagree with this being the most sophisticated though. Unless I'm missing something about this hack, the Stuxnet[1] architecture, complexity, and long term planning feel far more sophisticated than the SolarWinds hack. [1] https://en.wi…
The attack is unique in its usage of the supply chain. The malware is not 'sophisticated' in the same way stuxnet is because it has different goals. This actors goals align with stealth above all else, which is evident in both the design of the malware and the choice of the supply chain delivery vehicle. Also realize that the network comminication scheme used attempts to blend in with the legitimate SolarWinds softwa…
The malware keeps a "breadcrumb" trail of each machine it infects, and based on investigations by Symantec [1] it was determined that every Stuxnet sample from Natanz originated from outside suppliers.