In its basic usage, this script will modify the router such that blocked addresses are null routed and unreachable. Since the address blocklist is full of advertising, malware, and tracking servers, this setup is generally a good thing. In addition, the router will update the blocklist weekly. However, the blocking is leaky, so do not expect everything to be blocked.
The script must be copied to an OpenWRT router (gargoyle firmware works fine, too).
For example, if the router is located at 192.168.1.1: