Presumably you are asking because you have a child who resets the hub to overcome parental controls.
If that is the case and your child connects by wireless and not Ethernet cable, you could pick up a similar second hand BT Hub from ebay. They are usually fairly cheap.
Prior to doing the next paragraph you could plug it in, without it being connected to the phone socket or the ONT depending on what type of broadband you have, and it will transmit the wireless signal. You can connect to the wireless signal with your own wireless devices which will then be stored in your devices memory.
After doing that change the "new" hubs SSid (name) and password to be the same as the one you have at present. This will allow all the devices that presently connect to your network to connect to it without changing anything.
Remove/hide and do not divulge the "new" hubs SSid and password that is on the hub. Remember to keep a note of the details because you will need them in the future, in fact probably the same day that you connect it up.
Plug the "new" hub in and set it up with your present parental controls etc. All your networks wireless devices will seamlessly connect because you have given it the "old" hubs SSid and password and the parental controls will activate.
Your child will notice the parental controls are active and at some point carry out the factory reset as per his/her normal behaviour but on this occasion the factory reset will not be back to the "old" hubs settings, instead it will be to the "new" hubs SSid and password which he/she will not have. This will stop the child's device from connecting to the Internet.
If you did not previously connect your devices to the "new" hub you will have the correct SSid and password details so you can log your device onto it if need be.
Your child will obviously not have those details nor will he/she unless you give them to him/her which you will not do.
Once your child has carried out the factory reset you can point out that the connection is lost. All you will say is that the Internet is down because there has obviously been a factory reset of the hub. Do not mention the change of hub.
You will inform the child that you will only restore his/her use to it in your own good time or when they start to live by the house rules.
When you decide it is the correct time, you log back onto the "new" BT hub and again change the SSid and Password back to the "old" details resetting the parental controls and the connection will be restored to your child however it will be lost again should your child try another factory reset.
A bit of faffing about but other than locking the hub away or removing your child's devices there is not much else you can do that can't be easily circumvented by a computer savy child.
Your child will still be able to connect to BTWifi if they have your username and password so it would be worth changing your password for that.
