  Self-similarity is the property of a system being similar to a part of
itself. We posit that a special class of behaviourally self-similar systems
exhibits a degree of resilience to adversarial behaviour. We formalise the
notions of system, adversary and resilience in operational terms, based on
transition systems and observations. While the general problem of proving
systems to be behaviourally self-similar is undecidable, we show, by casting
them in the framework of well-structured transition systems, that there is an
interesting class of systems for which the problem is decidable. We illustrate
our prescriptive framework for resilience with some small examples, e.g.,
systems robust to failures in a fail-stop model, and those avoiding
side-channel attacks.
