It absolutely is possible to detect and that’s not an urban legend. While it’s theoretically possible to build a totally passive signal receiver, it’s not realistically how any kind of contemporary receiver will actually work. It will broadcast signals that are detectable and with the right knowledge and intuition about how that signal is getting produced can quite conclusively indicate all sorts of things you’d think would be totally private. CRT TVs in particular are well-known for absolutely blasting out electronic signals of all kinds as they seek, process, and display the image. There are many ways to detect not only that they simply exist and are turned on, but also what station they are tuned to and potentially even what’s on the screen without even being tuned to any over-the-air station.
It is even possible to detect what a car radio is tuned to, and it is in fact so possible there are even billboards and advertising companies that actually do this, roadside. For advertising, naturally. This is not new technology either. It has been known about for a long time.
We assume all these things are secure and not getting spied on because they ought to be, in an ideal world, but the reality is far from ideal and security through wishful thinking and obscurity is not security at all. The same kind of wishful thinking and obscurity on the other hand is an absolute playground for people want to detect and spy on things. Obscure tricks like this are widespread and it’s impossible to hide from what you don’t know about. Real security is hard work with diminishing returns, and perfect security is almost certainly unattainable.
And unless you think this kind of obscure observational trickery is limited to spying on us poor ignorant peasants, there was a report just recently that found a significant chunk of space-to-earth communication (including some military communications) is basically plaintext and being broadcast to everyone and anyone who knows where to look. Oops.
You can’t stop the signal, Mal. (Unless you build a Faraday cage, at least)
JohnEdwa@sopuli.xyz 5 days ago
en.wikipedia.org/wiki/TV_detector_van#Line-scan
You can’t really detect “TV signals”, but you can quite easily detect the 10.125 kHz horizontal line-scanning deflection coil of a CRT. Though I’m fairly sure even if they did originally start effective back in the 1950’s because people had very few elecronic devices around, actually detecting anything accurately must have been increasingly difficult as time went on, and a lot of the newer models must have been more about being a scare tactic.
shoe@feddit.uk 5 days ago
Scare tactics definitely play a part of it but, having seen official documentation covering up to reasonably recently (can say no more, sorry), I can confirm the technology did continue to evolve and detection was possible and the vans are real. I’m sure it’s continued to evolve since those old docs too, and I can’t say it was ever particularly effective, but there was some clever stuff at play from what I read!
Of course it’s all in aid of a horribly outdated principle, and I don’t approve of the scare tactics or intimidating nonsense letters, but I can appreciate some clever tech and documentation :)
Lumidaub@feddit.org 5 days ago
The German version of that very article says it’s not possible. Now what? w(°ｏ°)w
SolSerkonos@piefed.social 5 days ago
Uh, really? The English version is pretty convincing that it is- it even lists three different methods they used over the years. The sources seem convincing, but I’m quite literally judging the book by it’s title there.
Lumidaub@feddit.org 5 days ago
I know so very little about all this, I can only take people’s word for anything. ¯\(°_o)/¯