In visualisations, it is widely agreed that it is better to have more simple elements than fewer, complex elements (Tufte, 1990). A tree works well in situations where the structure is fairly simple and small. However, the attack trees that are used in TREsPASS are already more complex than can comfortably be fit on a screen. Working with and studying attack trees from a visualisation point of view, one can question the role of intermediate nodes. Other than being a labelled container for their child nodes, they are not actually steps along the attack path but nevertheless occupy a large part of the attack tree. We can visually simplify attack trees by turning them into linear sequences of their required children. This will result in more paths, but each path will be easier to follow. The simplification and conversion to straight paths benefit readability from a visualisation standpoint. One path now shows a user the steps that need to be taken in a straight and easy to follow line (although it does not usually imply a temporal or causal sequence).
Stacking Visual Elements
Another legend was also developed in the case that additional parameters to each step may be needed. By mapping different visual elements (thickness and colour to threat level) of a line to a scale of threat, it is possible to modularise this element and stack it to any number of parameters.
Visually, this becomes just as effective as the original legend because a step in which all parameters have a high perceived threat level will stand out much more strongly than a step with a low perceived threat level. When combined to form a path, this legend is very informative on which steps and connections are areas of vulnerability.