Silo focuses mainly on leveraging Oracle to obtain a shell and escalate privileges. It was intended to be completed manually using various tools, however Oracle Database Attack Tool greatly simplifies the process, reducing the difficulty of the machine substantially.

Arctic is fairly straightforward, however the load times on the web server pose a few challenges for exploitation. Basic troubleshooting is required to get the correct exploit functioning properly.

Optimum is a beginner-level machine which mainly focuses on enumeration of services with known exploits. Both exploits are easy to obtain and have associated Metasploit modules, making this machine fairly simple to complete.

Blue, while possibly the most simple machine on Hack The Box, demonstrates the severity of the EternalBlue exploit, which has been used in multiple large-scale ransomware and crypto-mining attacks since it was leaked publicly.

Legacy is a fairly straightforward beginner-level machine which demonstrates the potential security risks of SMB on Windows. Only one publicly available exploit is required to obtain administrator access.

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.

SwagShop is an easy difficulty linux box running an old version of Magento. The version is vulnerable to SQLi and RCE leading to a shell. The www user can use vim in the context of root which can abused to execute commands.

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.