Billion dollar idea - RoI, Radio on Internet!
Transmit Radio Signals via Ethernet
41–50 of 59 posts
Re: Transmit Radio Signals via Ethernet
#42Clever hack, but a lot of people are misinterpreting what’s going on here. These devices emit some very low level of 125MHz energy during normal operation. This software is simply turning that on and off, but not doing anything to increase the amount of emissions. Presumably the 125MHz emissions are within the FCC allowed envelope anyway, so this isn’t doing anything to exceed normal emissions limits. This only works…
125Mhz is the frequency you get with 100 base tx. It's basically the baud rate of 100mb plus the 5 bits to encode 4 bits overhead. 100 * 5/4 = 125.
As you mention, this is toggling the expected 125Mhz on and off. It's not noise, it's "the signal".
Re: Transmit Radio Signals via Ethernet
#43Please don't try this at home! 118 MHz - 137 MHz is a protected Aviation band across the globe for airplanes to communicate with air traffic control. We already have enough industrial noise problems in this band; please don't contribute to pollution of protected spectrum. You will be interfering with the safe operation of the airspace. See: https://en.wikipedia.org/wiki/Airband
This does not magically increase the power radiated by an ethernet cable or somehow change the base frequency of the interference. Furthermore, the power levels are very low. If you check the link at the bottom, he is using a directional (Moxon) antenna to receive this faint signal. If this could somehow pose an issue with anything, it would have been caught in EMI testing of all network equipment sold
It does not increase power. But it couples data instead of static noise into the communication which might be more annoying on the other end.
Re: Transmit Radio Signals via Ethernet
#44Please don't try this at home! 118 MHz - 137 MHz is a protected Aviation band across the globe for airplanes to communicate with air traffic control. We already have enough industrial noise problems in this band; please don't contribute to pollution of protected spectrum. You will be interfering with the safe operation of the airspace. See: https://en.wikipedia.org/wiki/Airband
Does regular usage of ethernet cables cause problems for aircraft?
Re: Transmit Radio Signals via Ethernet
#45Earlier quoted context omitted.
I've spent months and sleepless nights trying to get a product through the EMC certification. It's certainly possible but it's time consuming and expensive. With a shoestring engineering budget and a product that needs to be on the shelves in a month? Not really. I'm sure many devices on the market are not compliant. I follow lists of products removed from market for non-compliance and there are plenty each week. But…
Yeah, I remember in the early 2000s we had a wireless RCA audio/video transmitter, bought at a local electronics store, that played absolute havoc with the WiFi in our house as well as several neighbours. Another classic example is early cellphones that you would pick up on stereo systems etc. - "dat-dara-dat-dara-dat-dara-dat-dara-daaaaaa" going out in full blast.
In GTA 4 (set in the early 2000s or so) you hear that on your car stereo before your phone rings. I always loved that detail.
Re: Transmit Radio Signals via Ethernet
#46In college we had an I2C to ethernet adapter on our drone testbed that caused all sorts of RF interference for us. We eventually wrapped the whole fuselage in a farraday cage so that the datalink and flight controls wouldn't be overwhelmed. It was responsible for transmitting data at a 1 Hz rate, and we could visualize the interference on a spectrometer over a broad range of Rf at exactly 1 Hz. Anyway, we totally cou…
I thought i2c slowest clock was 100kb/s, how did this end up in a 1Hz rate?
Re: Transmit Radio Signals via Ethernet
#47As someone recently participated in an EMC measurement, I really don't understand how anyone passes these tests without some kind of cheating (using double-shielded, very expensive industrial cables + hacking with functional earthing).
Paying special attention to power distribution tends to help, along with encasing the product in something conductive. It's also really beneficial to have some kind of test equipment in house to get a general idea, think of it like having a debugger.
The first two options are somewhat expensive, the NRE for the power supply design isn't attractive to manager types and conductive coatings for plastic or a metal enclosure are not the cheapest options. But if you're dead set on compliance it's better to frontload the design costs instead of iterating 3 times before you get to market.
Re: Transmit Radio Signals via Ethernet
#48Very nice, could be used for exfiltration with some tuning. The most advanced example of this kind of inadvertent transmission I've seen is Fabrice Bellards DVB-T transmitting with a standard VGA card: https://bellard.org/dvbt/
https://en.m.wikipedia.org/wiki/Tempest_(codename)
I wanted to spin up a hardening service back in the mid-90s, based around what we knew of Tempest. I even named it Echelon Consulting (as in "upper echelon," but with a nod to ECHELON). My spouse wouldn't let me, they felt it'd be too risky to get involved with that environment, and we were just starting our family.
But... yeah. You could tune into VGA monitors up to a mile a way using consumer hardware, and reception is perfectly legal (lots of case history to back this up)!
I figured my pitch would be to walk in with a briefcase setup, flip a switch, and show them what the receptionist was working on. Then ask if they were worried if competitors could know what they were working on (not a threat, just bringing awareness), or would they be were interested in some expensive cables/hardware.
Now that the kids are grown up and divorce pending, I've debated getting back into the netsec field. Lots of fascinating angles to be had in unexpected hardware boundaries... and my background in data science/machine learning/DSPs could prove fruitful in signals reconstruction...
Re: Transmit Radio Signals via Ethernet
#49Previously posted here: https://news.ycombinator.com/item?id=25012469
Re: Transmit Radio Signals via Ethernet
#50This is a neat side channel attack for data exfiltration. The author is a radio amateur (Poland) and would do well to look at FT8 or other error correcting CW modulations other than simple Morse code. I would estimate you could pick up a signal at nearly a kM using such a scheme.