Second-Hand Television SHINEs, Takes Down Entire Village’s Internet

We occasionally get stories on the tips line that just make us want to know more. This is especially true with tech stories covered by the mass media, which usually leave out the juicy tidbits that would just clutter up the story for the majority of non-technical readers. That leaves us to dig a little deeper for the satisfying details.

The latest one of these gems to hit the tips line is the tale of a regular broadband outage in a Welsh village. As in, really regular — at 7:00 AM every day, the internet customers of Aberhosan suffered a loss of their internet service. Customers of Openreach, the connectivity arm of the British telco BT, complained about the interruptions as customers do, and technicians responded to investigate the issue. Nobody was able to find the root cause, and despite replacing nearly all the cables in the system, the daily outages persisted for 18 months.

In the end, Openreach brought in a crack team from their Chief Engineer’s office to investigate. Working against COVID-19 restrictions, the team set up a spectrum analyzer in the early morning hours, to capture any evidence of whatever was causing the problem. At the appointed hour they saw a smear of radio frequency interference appear, a high-intensity pulse of noise at just the right frequency to interfere with the village’s asymmetric digital subscriber line (ADSL) broadband service.

A little sleuthing led to the home of a villager and a second-hand TV, which was switched on every day at 7:00 AM. The TV was found to be emitting a strong RF impulse when it was powered up, strong enough to knock out the ADSL service to the entire village. Openreach categorized this as SHINE, or single high-level impulse noise. We’d never heard of this, but apparently it’s common enough that BT warns customers about it and provides helpful instructions for locating sources with an AM radio.

We’ll say one thing for the good people of Aberhosan: they must be patient in the extreme to put up with daily internet outages for 18 months. And it’s funny how there was no apparent notice paid by the offending television’s owner that his or her steady habit caused the outage. Perhaps they don’t have a broadband connection, and so wouldn’t have noticed the borking.

In any case, the owner was reportedly “mortified” by the news and hasn’t turned the TV on since learning of the issue. This generally seems to be the reaction when someone gets caught inadvertently messing up the spectrum — remember the Great Ohio Key Fob Mystery?

Thanks to [Kieran Donnelly] for spotting this for us.

Peel Apart Your ISP’s Router

Whether your home Internet connection comes by ADSL, fibre, cable, or even satellite, at some point in the chain between your ISP and your computer will be a router in your home. For some of us it’s a model we’ve bought ourselves and loaded up with a custom distro, but for the majority it’s a box supplied by our ISP and subject to their settings and restrictions. [Paddlesteamer] has just such a router, a Huawei model supplied by the Turkcell ISP, and decided to do a little snooping into its setup.

In a tale of three parts, we see the device unravel, from uncovering a shell to reverse engineering its update process, to delving in its firmware and finally removing all its restrictions entirely. It’s a fascinating process in which we learn a lot, such as the way a man-in-the-middle attack is performed on the router’s connection tot he ISP, or that it contains an authorised SSH key seemingly giving Huawei a back door into it. You may never do this with your ISP’s router, but it pays to be aware of what can be put in your home by them without your realising it.

The Golden Age of router hacking may be behind us as the likes of the Raspberry Pi have replaced surplus routers as a source of cheap Linux boards, but  as this shows us there’s still a need to dive inside a router from time to time. After all, locked-down routers are hardly a new phenomenon.

Via Hacker News.

ADSL Robustness Verified By Running Over Wet String

A core part of the hacker mentality is the desire to test limits: trying out ideas to see if something interesting, informative, and/or entertaining comes out of it. Some employees of Andrews & Arnold (a UK network provider) applied this mentality towards connecting their ADSL test equipment to some unlikely materials. The verdict of experiment: yes, ADSL works over wet string.

ADSL itself is something of an ingenious hack, carrying data over decades-old telephone wires designed only for voice. ADSL accomplished this in part through robust error correction measures keeping the bytes flowing through lines that were not originally designed for ADSL frequencies. The flow of bytes may slow over bad lines, but they will keep moving.

How bad? In this case, a pair of strings dampened with salty water. But there are limits: the same type of string dampened with just plain water was not enough to carry ADSL.

The pictures of the test setup also spoke volumes. They ran the wet string across a space that looked much like every hacker workspace, salt water dripping on the industrial carpet. Experimenting and learning right where you are, using what you have on hand, are hallmarks of hacker resourcefulness. Fancy laboratory not required.

Thanks to [chris] and [Spencer] for the tips.

Ethernet Over Telephone Wire

When [Bobo1on1] upgraded his Internet connection from ADSL to Fiber he ran into an issue of actually getting that speed to his desktop computer though his LAN setup. Before he had been using a telephone extension wire which ran from where the DSL entered the house, through a splitter, to his computer where the modem was located. Now that the router used by the fiber system is located at teh entry point, he has no easy way to run Ethernet cable to his computer room. Wifi is predictably slower than the 50mbit WAN connection, and he was unable to use the telephone cable as Ethernet directly.

The solution turns out to be a pair of TP-Link home plug adapters. These are designed to use your home’s mains wiring for data transfer. But [Bob] rigged it up so that they can push 224 mbits/sec over the telephone wire. Since you can’t run mains voltage through the telephone wire he had to hack a method to separate power for the devices from the data I/O. This was done with an external power supply and some passive components for filtering. The drawback is that this is half-duplex so up/down communications cannot happen at the same time.