TartarSauce is a fairly challenging box that highlights the importance of a broad remote enumeration instead of focusing on obvious but potentially less fruitful attack vectors. It features a quite realistic privilege escalation requiring abuses of the tar command. Attention to detail when reviewing tool output is beneficial when attempting this machine.

Brainfuck, while not having any one step that is too difficult, requires many different steps and exploits to complete. A wide range of services, vulnerabilities and techniques are touched on, making this machine a great learning experience for many.