Structure discarding short episode subsequences

[jzelenjak]

Description

The break_into_subbehaviors function, which is responsible for cutting episode sequences into episode subsequences, discards short subsequences, for example:

This check occurs multiple times within the function and it is also present in generate_traces function. Ideally, it should be only in one place (in generate_traces).

Furthermore, when splitting, if a sequence goes like [low, low, medium, high, low], then [low, low, medium, high] is saved but the last [low] is just discarded. We probably shouldn't lose alerts like this. On the other hand, it is not clear what to do with a single event either. Maybe we keep them regardless?

Proposed solution

• Leave only the check in the generate_traces function and update the break_into_subbehaviors function accordingly. The resulting attack graphs should be the same as before.
• For now, these short episodes can be discarded, as they used to be, and it will be left to the user whether they want to keep them or not.

[jzelenjak]

This is a bit tricky one, so it needs some discussion.

I think that this part can be safely removed:

For break_into_subbehaviors method, it is not that easy. A potential change could be something as follows.

This is the original:

This is the modified:

1. Because there have to be at least two episodes for a cut, sequences with one episode have to be either discarded or stored immediately, before cutting.
2. I don't know what to do with this part
   
3. The pieces part could be removed, so that it also addresses issue #28