A Feral Information Systems (FIS) is any technological artefact (e.g. spreadsheets) that end users employ instead of the mandated Enterprise System (ES). ES proponents suggest that the installation of an ES will boost productivity. However, Production Possibility Frontier theory provides insights as to why the introduction of an ES may instead suppress an end user's productivity. Structuration Theory offers insights that explain how certain end users may have access to powerful resources. Rather than submitting to the ES, the end user can employ FIS to block or circumvent aspects of the ES. Further, the concept of life chances helps explain why individuals may or may not develop the core skills required to construct an alternate to the ES, the FIS. In relation to the ES usage, an end user may adopt one of four Modes of Operation, namely: Submit, Dismiss, Hidden, or Defiant.