Have the commenters here extolling the virtues of these "obliterators" actually built one? Because they don't do much. Younger me made one ~20 years ago (actually around the time this page first came out!) and was very disappointed in how little it really did. Nothing happened to the hated DSL modem I wished destroyed! So what gives? It took me a while to figure it out, but these days I'm a professional EE and I have some insight....
Turns out the magnetics on an Ethernet port are good at their jobs. Like, really good. Not quite telecoms lightning-strike-survival good, but up there. Mains 60Hz may as well be DC as far as these things are concerned, and they're explicitly designed to block DC. Sure, for some configurations of magnetics you can blow them up if you get the pin connections just right, but that requires you to do a lot more than just "connect the transmit pins of the RJ-45 to HOT on 110VAC and the recieve pins to Common". Because that doesn't work. And even when it does work, it just overheats and pops the magnetics, opening them. Nothing happens inside the device proper.
If you want to cause some real fun you need a hi-pot tester plus a ground bonder. Those can do things that shouldn't happen.
A friend and I made one of these in high school and plugged it into everything we could find because we were complete idiots. Literally nothing broke. My iMac Rev B's CRT did go crazy while the device was plugged into the Ethernet port, but everything was fine afterwards. Why would I try to break my only computer? I have no fucking clue. Kids are dumb.
I mean, it's 5,000 volts at 100mA for the "high current" hi-pot or 20,000 volts at 10mA for the "high voltage" one or 40A AC @ 8V AC for the ground bonder. They do about what you'd expect: components pop, things arc, things arc a lot at 20kV, things smoke and then melt if you shove 40A through them.
It's more interesting when you break the tester itself. But then you have to fix the tester. These are not complicated machines (they're basically just transformers)... there's some complexity in regulating the outputs and more in making the measurements but most of the hard stuff is in having the tester itself survive the horrid abuse it's visiting on everything else around it.
I lost two Ethernet ports a few months ago from a lightning strike on a neighboring house. The devices still work otherwise and other Ethernet ports connected to the switch were unharmed. They were both on a PoE switch which may have been partially at fault (though it still works too).
A friend of mine was having a lot of really really weird network issues at one of their location in another city (B2B supply company). Ports randomly going up and down on various equipment over the network. Appeared to be an electric issue, so we did various testing, ground bonding, etc. Added redundant equipment after that failed to be reliable. Having little else to offer in the way of suggestions, I made a joke that someone was using an etherkiller.
Damned if I didn't end up being right. They had a clerk who was embezzling by creating false customer returns. Every time she made one she plugged the network into the mains. Her boyfriend apparently made this thing and told her that it would 'fuzz the system' or some other kind of idiotic idea. What it actually did was eventually start a small fire in the wiring closet.
So, yeah the effect of one of these things is gonna be highly dependent on the environment. The galvanic isolation of Ethernet is not any sort of guarantee. Though I can confirm that the Cisco gear stood up to unreasonable abuse, it was unequivocally damaged.
IIRC ethernet cable side is only magnetically coupled to the port/device side via small transformers. So running DC would probably just melt the cable or transformers but is not really likely to damage the device side (? Not actually sure about this).
But in this case it runs mains AC.. so... Do we expect the cable to blow first due to the high current, saving the device, or do would we expect the brief period of AC would cause enough induced current on the device side to also fry that?
Well ,first off, in POE powered devices it is connected to device, and I'd imagine in many cases (of being cheap) it would be directly coupled to device.
> So running DC would probably just melt the cable or transformers but is not really likely to damage the device side (? Not actually sure about this).
A step of voltage, whether that's just turning on AC on top of the cycle or just pushing DC thru it would go thru the transformer in form of short spike.
So sure, looking at random transformer data they are protected to like 1000Vrms so it wouldn't jump thru isolation, but initial magnetic spike might, and then it is up to any surge protection on the other side to ground that
> But in this case it runs mains AC.. so... Do we expect the cable to blow first due to the high current, saving the device, or do would we expect the brief period of AC would cause enough induced current on the device side to also fry that?
I'd guess transformer would be the highest resistance/area thing in the chain so it would melt first.
Depending on the implementation, but most probably it would burn the coils ("transformer") in the port, and probably the whole port module around, since the energies are high enough to burn quite a large chunk of material.
Cables are a lot thicker than the electronics inside the port itself, so my bet would be, port goes first, probably fails in a way that disconnects the current, if not, the ethernet cable would probably compete with the circut breaker on who melts first (circut breakers, even if they're marked with (eg.) 20A on them, survive a much higher current for a short time, before they eventually fail, due to some electronics, especially motors and large lightbulbs act almost like a short circut when they're starting up).
In well designed USB port you'd at least have diodes shorting it to ground/vcc.
But they are designed for ESD protection, so while high voltage, not that much energy
The problem is that there is no fuses, while ethernet basically have transformer working as a fuse, USBkiller can hammer the protection diodes till they burn out and then the rest of it gets it.
Turns out the magnetics on an Ethernet port are good at their jobs. Like, really good. Not quite telecoms lightning-strike-survival good, but up there. Mains 60Hz may as well be DC as far as these things are concerned, and they're explicitly designed to block DC. Sure, for some configurations of magnetics you can blow them up if you get the pin connections just right, but that requires you to do a lot more than just "connect the transmit pins of the RJ-45 to HOT on 110VAC and the recieve pins to Common". Because that doesn't work. And even when it does work, it just overheats and pops the magnetics, opening them. Nothing happens inside the device proper.
If you want to cause some real fun you need a hi-pot tester plus a ground bonder. Those can do things that shouldn't happen.