You can disable the checks if you want. Any application that uses the operating system API/DBus to evaluate network connectivity rather than building its own bespoke online check will probably break if you do, though.
Because all of these have to use HTTP, you can also easily override the standard network addresses in your hosts file and pick your own server if that's what you prefer.
http://connectivity-check.ubuntu.com/, https://nmcheck.gnome.org/check_network_status.txt, http://captive.apple.com/hotspot-detect.html, http://connectivitycheck.gstatic.com/generate_204, http://www.archlinux.org/check_network_status.txt, http://networkcheck.kde.org/
You can disable the checks if you want. Any application that uses the operating system API/DBus to evaluate network connectivity rather than building its own bespoke online check will probably break if you do, though.
Because all of these have to use HTTP, you can also easily override the standard network addresses in your hosts file and pick your own server if that's what you prefer.