Irked is a pretty simple and straight-forward box which requires basic enumeration skills. It shows the need to scan all ports on machines and to investigate any out of the place binaries found while enumerating a system.

Poison is a fairly easy machine which focuses mainly on log poisoning and port forwarding/tunneling. The machine is running FreeBSD which presents a few challenges for novice users as many common binaries from other distros are not available.

Node focuses mainly on newer software and poor configurations. The machine starts out seemingly easy, but gets progressively harder as more access is gained. In-depth enumeration is required at several steps to be able to progress further into the machine.