This topic

Neighbour intercepting our internet full-fibre junctiojn box on our outside wall

RoadWarrior — Tue, 03 Mar 2026 15:16:02 GMT

I have an interesting problem.

I have a full-fibre (FTTP) internet connection via BT and Openreach. Today that connection dropped for several minutes, so I started investigating. I found a person outside our house fiddling with a junction box on the wall. He claimed to be a "BT engineer", but could not provide any ID and his van was generic grey, not branded with BT or Openreach.

He said that he had "cut our connection cable by accident" and he would fix it immediately. Sure enough, our internet connection came back a couple of minutes later. But now there's a new cable running from this junction box to our neighour's house.

BT online chat wasn't very helpful - said they were investigating and then stopped responding. Is this actually an Openreach issue given that they're responsible for the physical infrastructure? And is any crime being committed here?

Re: Neighbour intercepting our internet full-fibre junctiojn box on our outside wall

gg30340 — Tue, 03 Mar 2026 15:37:01 GMT

Other Providers can use the Openreach infrastructure so it mat have nothing to do with BT or Openreach.

It may be that the person was a contractor for Openreach and everything is genuine however you should contact Openreach and report what has taken place.

You could always ask your neighbour if they were getting Fibre installed to see what they say.

If it is unauthorised Openreach should be able to investigate.

Openreach Equipment | Help and Support

Report Unsafe or Damaged Openreach Equipment – Safety Reports

Re: Neighbour intercepting our internet full-fibre junctiojn box on our outside wall

iniltous — Tue, 03 Mar 2026 15:52:25 GMT

You can get ( but it’s pretty rare ) external CSP’s (the junction box on the wall you refer to ) where they are designed to have 2 or 4 output terminations , a typical application is a small MDU , like (for example ) a building with 2 downstairs flats and two upstairs flats , instead of having 4 cables from the telegraph pole or jointbox in the footpath each with a CSP on the external wall , it’s effectively a single multi output CSP with a single cable input ( with 2 or 4 fibres inside, a Y cable or X cable ) and eventually upto 4 cables exiting it , one to each flat in this example , so less plastic CSP boxes on the wall and less individual cables to the CBT

If the neighbouring property is the other half of a pair of semi detached houses , then it may be they took advantage of the fact there was a ‘route’ existing from the house wall to the CBT in a jointbox , and they utilised it , even though it meant getting inside the CSP that was provided when your FTTP was installed, if the CSP is pretty much on the boundary between your property and next door this may have been the way service was always envisaged, or possibly the underground route to the other property was unusable (without excavating) and using ‘your’ CSP a convenient way to get around their blocked duct and give service without any delays.

In any event the fact your service has come back on , I doubt it’s anything to worry about , apart from the potential trespassing to get to the CSP .

Another possibility alluded to , if Alt Nets are in the area , and the neighbours ordered service from them , they may have used your service to make provision of their service easier, wether that’s allowed or not , but they haven’t ’cut in’ to your cable and joined an extra one to it , fibres don’t work like that .

Re: Neighbour intercepting our internet full-fibre junctiojn box on our outside wall

RoadWarrior — Tue, 03 Mar 2026 16:06:51 GMT

Openreach declined to investigate on the grounds that there is no visible damage to the outside of the CSP or to the cables - and my internet connection is working normally. My neighbour declined to respond - he's a dodgy character.

Re: Neighbour intercepting our internet full-fibre junctiojn box on our outside wall

licquorice — Tue, 03 Mar 2026 16:12:45 GMT

One thing is certain, he won't be 'intercepting' your internet connection. That is only available to an ONT with your serial number.

Re: Neighbour intercepting our internet full-fibre junctiojn box on our outside wall

brookheather — Tue, 17 Mar 2026 16:22:35 GMT

You can check whether your neighbour has had an OpenReach ONT installed by using the BT checker:

https://www.broadbandchecker.btwholesale.com/#/ADSL/AddressHome

If a second optical cable was spliced onto your cable to provide your neighbour with FTTP then I assume it would require proper optical splicing equipment so unlikely to be someone "dodgy" installing it.

Re: Neighbour intercepting our internet full-fibre junctiojn box on our outside wall

licquorice — Tue, 17 Mar 2026 16:33:06 GMT

You can't just simply splice another fibre to the connection and as previous post, it wouldn't be of any use anyway without an ONT configured to match the serial number of the OP's ONT.

Re: Neighbour intercepting our internet full-fibre junctiojn box on our outside wall

WSH — Tue, 17 Mar 2026 16:57:54 GMT

I thought this thread was closed already?

A “fibre” carries multiple signals anyway.

With Openreach, I believe there can be up to 30 separate connections on each main fibre. The light is then split up by prisms and a separate sub-fibre, as it were, goes to each house. However, each of those fibres still carries all 30 data streams. Each data stream is encrypted separately and keyed to your particular ONT. This is why you can’t just connect any old ONT and why Openreach registering the correct serial number is so important.

Even if the neighbours are sharing the same fibre cable, they won’t be sharing the same data stream and they will not be able to see your traffic.

It’s a well-established technique. I’ve never been a Virgin customer, but I believe Virgin were using the same technique with their HFC system years ago.

Edit: Oops. Seems Licquorice slipped in in front of me there.