The CI system is a jenkins instance on http://ci.netsurf-browser.org/
The old discussion on Autobuilder requirements — lists requirements for the new autobuilder.
The master instance is a VPS provided by Mythic beasts.
A VPN between it and all the build slaves provides a network where no machines are publicly accessible. This is in addition to the ssh based tunnels used to copy data between CI nodes.
The Jenkins install on the master server is a snapshot release version
The majority of the build slaves are provided by our own virtual host server excepting operating systems which cannot be virtualised (principally MAC OS X).