[soci]

a) Can you point to an article were I can learn more about examples of big US corps being attacked by US sponsored actors?

It's a quite interesting topic indeed.

[peterkelly]

NSA infiltrates links to Yahoo, Google data centers worldwide, Snowden documents say

https://www.washingtonpost.com/world/national-security/nsa-i...

We can assume that the US government is not the state-sponsored actor in the OP, because their attack has already been publicly known for some time. This one is probably China or Russia.

[pquerna]

Does NSA tapping Google's fiber count: http://www.bbc.com/news/world-us-canada-24751821

[jedberg]

It's rarely written about, in part because the private companies don't want to share details.

Buy a beer for someone who has worked security for a big firm and they can tell you all about it.