How to get rid of ads in the browser?

Question

Computer networks

Good day. The problem is generally standard and its solution can be easily found on the Internet. Of course, I came across such malicious software, if you can call it that, and got rid of it "in a couple of clicks." But now the problem has taken on a different color. :) In general, there is:

1. 4 PCs with Windows XP installed,
   
2. 1 PC with Windows 10 installed,
   
3. 1 Macbook Pro (model doesn't matter) with OS X El Capitan installed,
   
4. 1 Dell Inspiron laptop (model doesn't matter) with Windows 10 installed,
   
5. 1 Router ‎Sagemcom 2804.
   

Attached screenshots to avoid unnecessary lines :) :
https://www.dropbox.com/s/yjtl5kktgyp3u8w/1.png?dl=0
https://www.dropbox.com/s/lohek6p7mippm1f/2.png?dl= 0
A network is established between all PCs. Laptops are connected via Wi-Fi. On a PC, this software is not detected, only on laptops. The browser does not matter - there is no banner only in Tor (installed many different browsers). The banner appears on these laptops only on this network. The pages on which the banner appears are selective (as an example: google.com, vk.com, yandex.ru).
I can not reset the router settings as there is no access to it.
Thanks in advance. :)
I apologize for the links, for some reason the regular means failed to load the image. I often encounter this problem in Safari on Toaster.

Answer 1

First of all, check the browser add-ons, remove any that you did not install yourself.
Second, check the hosts file.

Answer 2

"I can't roller-skate, help me set it up. Both legs are covered with gangrene, but there is no way to operate. What to tweak in roller skates?"
You obviously have a trojaned router. What does it mean - no access? Do you use stolen internet, all this park? Well, then, do a favor to the owner - help him treat the device, you see, you won’t have to steal ...