Over the past few years, many homes have become so dependent on web-connected devices that they need to leave the Internet connected around the clock, particularly for devices such as VoIP, remote desktop access, cloud-based backup and even web-connected household appliances such as the Nest Thermostat and Protect smoke/carbon monoxide alarm.
With the growing number of web-connected devices and household appliances, we often hear about the risks these face such as them becoming compromised, including web-connected baby monitors and CCTV cameras using the default password. However, many users still forget about some rogue clouds that even the strongest passwords and firewall security updates will not protect against and this time we’re talking about the real thing - Thunderstorms with cloud to ground lightning.
Most home Internet connections are carried over a phone line or coaxial cable, which provides a electrically conductive path to the home. Even Fibre to the cabinet (FTTC) connections still rely on a short length of copper wire running to the home, which is enough to provide a path for a nearby lightning strike to follow. In most cases, lightning just becomes a nuisance causing the DSL or cable connection to loose sync for a minute, however, with a near enough strike, lightning can cause serious damage.
About a week ago when there was a fair amount of lightning activity here, a neighbour nearby called me to talk about a problem she had. After a bright flash of lightning, she heard what sounded like a crockery pot shatter in her hallway just a split second before a fierce bang of thunder. When she went out, she saw fragments of scorched plastic and strands of wire about the place and the telephone socket blown apart. The following is the remains of the phone socket:
The DSL/phone filter was obliterated with some fragments shown below along with bits collected from the socket:
Unsurprisingly, the DSL router did not survive and had the familiar burnt electronics smell, although there was no visible damage on the outside. When she had someone visit to investigate the damage before I came, the person tried powering on her computer which had a network connection to the router and she said that sparks flew out of the computer and the keyboard (at least what she claims) followed by a bang and a puff of smoke. So it is pretty clear that the lightning made its way through the PC’s components. Luckily it was a fairly old computer (probably 10+ years) and she did not have anything else attached to the router.
So no matter how heavily one depends on having an always-on Internet connection, unless they are using an Internet connection that lightning cannot conduct down, the best protection is to unplug the incoming connection at the first sight of an on-coming thunderstorm or when thunderstorms are forecast before leaving the home or heading to bed.
A fibre to the home connection is immune to thunderstorms as the fibre is not conductive and is also immune to the electromagnetic interference that usually interrupts DSL based connections. However, while fixed wireless connections may also appear immune, it is still possible for a nearby strike to have a branch hit the externally mounted aerial in a similar way that roof mounted TV aerials occasionally get struck. The same applies for wired network connections going outside the home, such as to a detached building or outdoor network CCTV cameras.
For those who simply cannot disconnect from the web and need protection from lightning, one option is to get an adequate surge protection power strip with phone connections or network connections in the case of a cable or fixed wireless router. These are fairly affective from all but intense surges down the phone line or cable connection. Another option is to run all Internet connectivity over Wi-Fi. 802.11n provides sufficient bandwidth for most home Internet connections up to around 100Mbps sustained. Faster connections are generally delivered by fibre to the home, which is natively immune to lightning anyway. Obviously surge protected power strips are still required to offer some protection against spikes coming down the power line.
While the above is the most destructive damage I’ve seen lightning do although I've heard of much worse damage, I have seen at least 3 previous cases where lightning ruined someone’s router, all of which blew the network card in the PC, although the computer itself survived in each case.
