Internet users, content providers, and ad blocker developers are in a constant arms race. Users have deployed ad-blocker web browser extensions for years, and these extensions work quite well for standard web pop-ups and banner ads. But browser extensions are a little more trouble to implement on cell phones and other mobile devices. Also, ads built into apps typically remain untouched by the filters imposed by browser extensions. In addition, conventional ad blockers do nothing to stop modern Internet-connected devices like smart TVs, stereos, and even washing machines from transmitting data to the Internet in a very talkative way.

Other alternatives have developed in recent years to give users new tools for stopping Internet ads in a more global and comprehensive way. Pi-hole [1] is a promising tool that provides a centralized means for stopping Internet advertisements across a local network. The Pi-hole developers refer to Pi-hole as a "black hole for Internet advertisements." In more technical terms, Pi-hole is what is often called a "DNS sinkhole" [2]. A DNS sinkhole is a DNS server that gives out unroutable IP addresses for domains that are listed in a "sinkhole" list, which is basically a blacklist. Because Pi-hole leverages a standard process that is built into all TCP/IP networks (the DNS lookup process), it doesn't require any client applications or special configuration, other than to point the client to the Pi-hole DNS server, which can happen automatically through DHCP.

Sinking the Putt

Pi-hole combines common Linux-based network tools such as the DNS forwarder dnsmasq with a lighttpd web server and other Linux tools. As the name suggests, many users install the program on a Raspberry Pi. In addition to Raspbian, the project also supports Debian, Ubuntu, Fedora, and CentOS (see the box entitled "Pi-hole on Linux").

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