The networks need to be broken - just blacklisting won't stop the OPs devices connecting to the "other" network. The powerline adapters need to be properly secured so that they are on a different network than the neighbours. As it stands everything on both networks can see each other (or would take minimal change to allow them to).

HomePlug units can vary their encryption either by pressing a button on the allowed devices in a short time frame or using the built in software to talk to your own plugs.

Doing that should stop them being able to hop onto the LAN running over the HomePlugs

Indeed - and that is what the OP needs to do - they don't need to blacklist or change settings on the router they just need to break the link with the neighbours power line.

Personally once the link is broken I would also be changing the passwords on the router as it is possible the neighbour could have got hold of those - unlikely but may as well be safe.

Personally when I used homeplugs I set my own secure password on them rather than using the buttons to do the auto encryption - that way I had control and I like to have control over my network.

The other issue will be that they will be "interfering" with each other and thus restricting the bandwidth on each network. Easy enough to sort out the LAN connection issues, but little can be done to stop the interference.

I wonder how close the power networks are. They would need to be on the same phase and be connected very close to the metering point which itself would need to be close to the CUs.

BBUK

First configure access control.

Go to settings and access control, enable access control, then block each device between 02.00 and 01.30. This will get your bandwidth back quickly.
I use this feature to control when my kids can use the internet on each device. Helps them sleep when they cannot be on the internet after 10pm and get their homework done if I can block games devices at certain times.!

If you go to advanced settings and look at Home network you can see all devices that have been connected, if you refresh you will just get all those connected at that point in time.

You should also change the password on your hub to prevent other people accessing it and changing the settings.

You can then reset the homeplugs following the Homeplug instructions so that only yours are linked. ( Different sets have slightly different ways to change the encryption on them).

I disagree. Fix the homeplugs - the access control is irrelevant as if they aren't on the network then they won't be using bandwidth.

i am still surprised that home plugs can go from one house to the next.

In reply to a post by zyborg47:

i am still surprised that home plugs can go from one house to the next.

I'm not, if they are on the same supply circuit. What I am surprised is how weak the security is when using them out of the box.

It does suggest they are using the same key from the factory. I am not surprised that 2 devices in the same package have the same key but more surprised potentially that all devices have the same default key (or all devices from the same manufacturer).

I suspect now that all devices are configured the same when they leave the factory so if you pick up several different sets of powerline devices they will connect straight away without any configuration - that is a definite security hole (partially mitigated by the fact they don't cross phases so the number of people on the same "electrical circuit" would be limited.

I have been in this house from new, for 47 years.

it is the western-most one of a terrace of four, with the sub-station clearly to the east, about 200 Metres.

I recently obtained the local distribution map from the electricity supplier; and was surprised that it clearly showed the supply going from the common footpath, in to the immediately adjacent house, say #2, then back out again to my house, say #1.

Speaking to the "neighbour" in #4 at the other end, he was aware that his supply similarly went in to #3, to come out again to his house, #4.

Several years back, he had a problem; and like myself, thought that his supply came "straight"; but the repairing electrician after checking Fuseboard etc in his #4, said that he would have to go in to #3, as #4's supply came via that - thus effectively confirming the similar diversion for my house.

Good thing that #3 neighbour was at home that evening!

The only reason I can think of, was to avoid having some form of jointing box/es in the footpath.