I am not a physicist, but that's detecting reception of (I think FM) UHF and requires specialised equipment. Detecting Wifi which uses a spread-spectrum modulation at a higher frequency would be even more difficult. Add to that the existing, allowed Wifi networks that probably already exist which overlap the banned ones.
The real problem in security is usually human factors — loose talk, spies, informers, interrogation — not technological ones.
But the thing is that using a wifi node is not passive reception. And while wifi uses spread spectrum, in order to be accessible to the people you want to reach, you'd need to make it available using common protocols. The authorities need only go war driving for these nodes, connect and then watch the tcpdump output. Corporations do this now to detect rogue access points, so I don't think it's beyond the means of a sufficiently motivated government.
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I am not a physicist, but that's detecting reception of (I think FM) UHF and requires specialised equipment. Detecting Wifi which uses a spread-spectrum modulation at a higher frequency would be even more difficult. Add to that the existing, allowed Wifi networks that probably already exist which overlap the banned ones.
The real problem in security is usually human factors — loose talk, spies, informers, interrogation — not technological ones.
But the thing is that using a wifi node is not passive reception. And while wifi uses spread spectrum, in order to be accessible to the people you want to reach, you'd need to make it available using common protocols. The authorities need only go war driving for these nodes, connect and then watch the tcpdump output. Corporations do this now to detect rogue access points, so I don't think it's beyond the means of a sufficiently motivated government.