A Map of the Spamiverse
IP addresses of hosts connecting to our main MX mapped to a 512x512 pixel grid. Each pixel represents one /18 network. The bits from the IP address are alternatingly mapped to the X and Y axis, so a network always forms either a square or a rectangle with a width/height ratio of 2:1. Thus the upper half is 0.0.0.0/1, The lower left quadrant is 188.8.131.52/2 (the former range of class B networks), etc. The almost full square in the upper left quadrant is Comcast, the not quite so full to the left of it is AT&T. The block at the lower right is East-Asia.
The color of the pixels is determined by the results of the SMTP transactions: Success increases the green component, temporary failures (e.g. because of greylisting) increase the blue component, and permanent failures (e.g. attempts to mail to an unknown address) add to the red component.