The FREE Cybersecurity Glossary by Thor Pedersen!

Harrison-Ruzzo-Ullman model: A formal model used for expressing access control policies and analyzing their security properties. Named after its creators, Michael A. Harrison, Walter L. Ruzzo, and Jeffrey D. Ullman, the model focuses on determining whether a system configuration could allow a subject to acquire unauthorized access rights. It's particularly known for its undecidable safety problem - it's not generally possible to determine whether a given system is 'safe' against privilege escalation.

High-level languages: Programming languages that use a more abstract and human-readable syntax, as opposed to low-level languages that use machine-readable instructions. They are commonly used by software developers to write complex programs or applications, as they are easier to read and understand than low-level languages. Examples include popular high-level languages such as Python, Java, and C++.

HOTP (HMAC-based One-time Password): An algorithm that computes a one-time password from a shared secret key and an incrementing counter. In a security context, this provides a robust method of two-factor authentication, enhancing user verification processes by generating unique, counter-based credentials that are difficult for attackers to replicate or predict, thereby protecting sensitive data and system access. HOTP uses a counter to produce credentials, which do not rely on a clock to change credentials after a set time. The "one-time" element simply means the credentials are meant to only be used once and are invalid in the future.

Hybrid Identity as a Service: Hybrid Identity as a Service (IDaaS) refers to cloud-based solutions that manage user identities and access across both on-premises and cloud applications. It combines the advantages of on-premises identity solutions with the flexibility of the cloud, allowing users to employ a single identity or set of credentials to securely access resources regardless of location.

Hybrid self-hosted: A system configuration where part of an organization's data or services are maintained on their own servers (self-hosted) while other parts are hosted on third-party servers, often cloud services. This allows organizations to maintain control over critical or sensitive data or applications while still leveraging the scalability, accessibility, and often cost-savings associated with third-party hosted services.

H.323: H.323 is an ITU-T standard for audio and video communication over IP networks such as the Internet or corporate LANs. It provides a framework for multimedia conferencing and includes specifications for call signaling, media transport, and control. H.323 is used by various software and hardware to enable video conferencing and VoIP communications. Note that while Skype, Cisco WebEx, and Zoom may use similar protocols, they do not all specifically use H.323.