The Internet has become an advertising platform. Users of mobile devices are acutely aware of this, because mobile operating environments and apps force ads on their users, in addition to those that pollute the Web. It’s getting harder to avoid the ads on Android handsets, as Android is increasingly locked down and difficult to customize. It’s certainly not in Google’s interest to make it easy to block ads.
If you block ads at the system level, all apps – and the system itself – are protected. Moreover, methods for blocking ads can usually be extended to protect against trackers and other kinds of malware.
So far as I know, all system-level ad-blocking methods work by overriding DNS behaviour. DNS (domain name service) is the technology that maps hostnames to numeric IP addresses; a DNS lookup is the first step in almost all network operations.
