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I worked for a company that was acquired by Lockheed. I ran IT and had already spent a few years 100% rebuilding the infrastructure of the company when I joined.
As we were assimilated I worked with IS&S and their security teams closely to ensure our security measures were up to snuff with Lockheed's requirements (we built the RFID tracking system the military used for shipping pretty much everything) In our security meetings, we were briefed on activities that were happening, what we needed to do and why.
China was constantly attacking Lockheed and all other defense contractors.
They were pretty sophisticated in how they did it; targetted spear phishing was one of their successes:
Chinese spies would attend defense contractor events - meet and seek out lockheed and other employees. Get their business cards and spoof mail from one employee to the other, referring to events that occured at the convention to get people to click on shit that would be a trojan. These trojans were rather sophisticated in that they would operate very very slowly to trickle pieces of information out. Sometimes they were very specific pieces of information.
I don't recall exactly how this was found out, but someones machine was being checked out - and in the process the trojan was found. When the chinese were alerted to the fact that the trojan had been found, they turned whatever their bot-net was up to 11 and attempted to just mass send out as much data as they could.
(All of lockheed only has (I think) 3 connections to the internet)
They cut it off and had to get rid of these trojans.
Another time, a supplier (I think it was in Taiwan, I cant recall exactly) a supplier was hacked and its machines would install stuff on any USB sticks used.
Lockheed machines were not allowed to connect to non-lockheed networks, via Wifi or any other means. So they would use USB sticks to transfer stuff.
The chinese went after the suppliers machines as a vector to get connected with the lockheed machines. I have mentioned this stuff here on HN before, and in light of China's 50-100 year vision for where they want to be, we are basically fucked. The chinese have been securing access to all major natural resources in Africa, as well as being the manufacturing hub for EVERYTHING - while the US government is squabbling over petty short term profit efforts and securing a diminishing resource (oil).
This is not to say the US is some slouch in the cyber security space; Stuxnet and Doqu are clearly US/Israel cyber attacks that are amazing. But anyone would be a fool to not be very wary of where the online digital war is headed.