You are looking at, more or less, a portrait of the internet over an average 24 hours in 2012—higher usage in yellows and reds; lower in greens and blues—created by an anonymous researcher for the "Internet Census 2012" project. How, exactly, do you gather this much data? Well: not legally, that's for sure.
In order to track the geographical location and usage patterns of the internet, our researcher created a "botnet"—a network of nearly half a million hacked computers, chosen from a selection of Linux machines with no or default passwords, pinging everything they could and reporting back. The researcher says one of the chief concerns of the project was to "be nice"—"[W]e did not change passwords and did not make any permanent changes... We also uploaded a readme file containing a short explanation of the project as well as a contact email address"—but the botnet, dubbed "Carna," was ultimately highly illegal.
It's also not quite comprehensive. The computers being pinged to gather the data were limited to to IPv4 address space—leaving out the newer IPv6 protocol. But it still paints a extensive picture of the geographical internet. Here's another map showing the location of reachable computers across the world:
Update: some confusing wording about what the botnet was and did has been clarified.