Yes.

Thanks for all the above. I have reset my modem-router's configuration file back to its factory settings, but after altering in a text editor my online username and password for my ISP, it is probably exactly the same as it was previously. It is still 293 lines long, for example.

As it is slightly more understandable to adjust the settings in the config file rather than using its GUI, I have searched for all lines that mention DNS or DHCP. (Perhaps DHCP is irrelevant, but I am ignorant about this). Here they are:

alpha set /misc/u32max_dhcp=3232236030
alpha set /misc/u8AutoDNSRELAY=1
create ppp intf ifname ppp-0 startondata mru 1500 lowif aal5-0 droute true ppoa outside usedns true extifindex 210000 inacttimeout 30 cpeipindex 1 mtu 1432
modify dhcp server cfg enable
create dhcp server pool start-ip 192.168.1.3 poolid 0 end-ip 192.168.1.65 mask 255.255.255.0
create dhcp relay intf ifname ppp-0
create dhcp relay intf ifname eth-0
create dhcp relay intf ifname usb-0

More of the config file can be seen up this thread.

Does anyone understand these config file lines and could tell me what to do to adjust them so that the DNS lookup is done with 8.8.8.8 and 8.8.4.4 please?

My IP address changes every time I log on, so I think that means I have a dynamic something.

Thanks.

i do not understand all, but i can say for sure that none of these lines defines a dns server.
afaiu, "create dhcp server pool start-ip 192.168.1.3 poolid 0 end-ip 192.168.1.65" refers to the dns server pool that is being presented to the connected computers, i.e. you could probably use 192.168.1.9 (or any address in the range defined) as a dns server, but where the router gets IPs resolved it doesn't say. (*)

on a side note i must say i don't understand why you so desperately want to use google's nameservers, with so many non-exploiting alternatives available.
you're probably much better off using whatever your IP provides you with.

(*) notice my frequent use of conditionals.
if you're not 100% sure, i'd suggest you not tinker with it.
unless of course that's what you want - see how far you can go with half a clue.

again, why do you think 8.8.8.8 is not in use?

I have now successfully switched the DNS server, and this has survived me restarting the computer and modem-router two or three times, so problem solved. Modem-router passwords also changed.

ISPs are now required to record your internet history, but the ISP is repeatedly being hacked. Different incidents are reported in the press every few months, and this will not include the events they are not aware of or keep quiet about. In addition, I am frequently rung up by scammers due to a lot of personal details being stolen from the ISP's overseas call centre. Twice this week for example. At first the scammers spoke good english and were articulate, now they speak bad english and are inarticulate. I imagine this means the stolen details are being sold to or copied by a lot of different scammers who are trying their luck. I expect the ISPs still have ways of recording the internet history even if you don't use their DNS server. It is like the Post Office reading through every letter they deliver to you, something they have not done for two or three hundred years I imagine. I was burgled once, it is best to improve your security before being burgled rather than after.

Thanks.

Edit: Although both the command "nslookup google.com" and the command "cat /etc/resolv.conf" still return 127.0.1.1.

it always baffles me how people think that using google services would actually improve their privacy....

I would be happy to have my privacy details split between the ISP and the DNS, because while they would both be easily available to governments, a hacker would have to hack not just one but two separate organisations and in addition would also have to collate the millions or billions of records together.

well i don't know about 8.8.4.4, but 8.8.8.8 is definitely google's nameserver.
i use opennic.

8.8.8.8 and 8.8.4.4 are the two Google public IPv4 nameservers.