The computer does all the listening for you. Just how good these systems are is a secret but the HA100 is being used by NATO nations right now. And
what the HA100 can not do the next version will. From what I understand the key so far for keeping everyone from having this tech is the computer
program that is the real key to decoding all the incoming signal data. Now if and when someone else comes up with there own software or get their
hands on something like the HA100 then it could change everything.
A whole new idea for stealth is going to be needed to counter this tech. .
Current stealth works by absorbing radio signals or scattering them. Maybe something of magnetic field that would allow the radio signals to go around
the craft might counter this but the tech for such a magnetic field does not exist yet but I bet someone is working on it this every minute.
color me not convinced, until such time as the US stops deploying stealth then i'll believe in the efficacy of this passive detection thing . to
get back to the OP, it sounds to me as if the article intends to influence the reader that the US should spend more on defense coz otherwise China,
Russia and other countries might outstrip them.