How can I change the file on a wi-fi router?

Question

Computer networks

Good afternoon! There was a need for a home Wi-Fi network, when downloading a file on the network, replace it. That is, let's say the client wants to open or download the file www.sait.com/data.txt and a file is loaded from www.my-fake-sait.com/data.txt to it. I know that this can theoretically be implemented by changing the DNS on the router how else can it be done? Thank you. Naturally, there is access to the router.

Answer 1

Set up a transparent Squid proxy on the router and set rules. If you interfere with https, you will have to put your certificate on your wife's computer.
Not every router will pull this, there may simply not be enough space.
You can also make NAT - wrap traffic to your proxy, standing on a separate machine. This will work on a weak router, but will require the use of an additional computer.