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The technology, which the agency has used since at least 2008, relies on a covert channel of radio waves that can be transmitted from tiny circuit boards and USB cards inserted surreptitiously into the computers. In some cases, they are sent to a briefcase-size relay station that intelligence agencies can set up miles away from the target.
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In most cases, the radio frequency hardware must be physically inserted by a spy, a manufacturer or an unwitting user.
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I am not sure how credible their sources are on this story, however if it turns out to be true then the people wearing tinfoil hats may not actually be crazy
Well, then it's a good idea to stuff your offline machine outside the reaches of any radio waves. Underground. Copper mesh cage. Behind 3 meters of steel reinforced concrete.
Alternatively, you buy computer parts and assemble it yourself. Anyone who has done any type of bitcoin / alt-coin mining knows how to do this: motherboard, ram, cpu, sata hard drive, etc. The NSA would have to insert the evil hardware into raw computer parts that you would not fail to see unless it was microscopic.
The relay station it communicates with, called Nightstand, fits in an oversize briefcase, and the system can attack a computer “from as far away as eight miles under ideal environmental conditions.”
Make the environmental conditions not ideal. You wrap your little offline computer in tinfoil, or lead or some other heavy metal, I don't know how anything can get anything from it farther than 8 inches.
