Every field has a vocabulary, and security is no exception. Before any technique makes sense, a learner needs a shared set of terms: what we protect, who might attack it, how they get in, and what we do about it. This category gathers those definitions so the rest of the library has a common language. It anchors the Foundation pillar because these ideas combine into the single concept everything else serves, which is risk.
The topics below define the essentials.
CIA triad names the three properties, confidentiality, integrity, and availability, that together define what it means for a system to be secure.
Assets and attack surface describe what security protects and the sum of points where it can be reached or attacked.
Threats and threat actors cover what a threat is, the kinds of actors behind them, and their motivations and capabilities.
Vulnerabilities and exploits draw the line between a weakness and the code or technique that abuses it.
Controls and countermeasures explain how preventive, detective, and corrective measures reduce risk.