Certification terms: H
178 study terms starting with H.
178 terms
- H.225The H.323 protocol for call signaling (Q.931-based, TCP 1720) and Registration, Admission and Status (RAS, UDP 1719).Advanced
- H.239The H.323 standard for sending a second video stream, such as presentation content, alongside the main camera video.Advanced
- H.245The H.323 control protocol that exchanges capabilities, determines master/slave and opens logical channels for media.Advanced
- H.264 (AVC)The ITU-T and ISO video compression standard (MPEG-4 Part 10 Advanced Video Coding) used by most conferencing systems.Foundational
- H.265 (HEVC)High Efficiency Video Coding, the successor to H.264 that delivers similar quality at roughly half the bit rate.Intermediate
- H.323An ITU-T umbrella standard for multimedia communication over packet networks, comprising H.225, H.245, RAS and codecs.Intermediate
- H.323 GatekeeperAn optional H.323 component that performs address resolution, admission control, bandwidth management and zone management.Advanced
- HacktivistA threat actor who attacks to promote a political, social or ideological cause rather than for profit.Foundational
- Hadoop Distributed File System (HDFS)Hadoop's distributed file system, which splits files into large blocks replicated across DataNodes, with a NameNode tracking metadata.Intermediate
- Half-DuplexCommunication in which a device can either send or receive at any moment, but not both at once.Foundational
- Half-Open Date RangeA date filter written as >= start AND < end, which includes the start and excludes the end so datetime values are captured correctly.Intermediate
- HallucinationWhen a generative model produces fluent output that is false, fabricated or unsupported by its sources.Foundational
- Hamming Quasi-Cyclic (HQC)Code-based key encapsulation mechanism selected by NIST in March 2025 as a backup to ML-KEM.Advanced
- Hammock ActivityA summary activity that groups related activities and spans their start and end dates.Advanced
- Hard Disk Drive (HDD)A storage device that records data magnetically on spinning platters read by moving heads.Foundational
- Hard LinkAn additional directory entry that points to the same inode as an existing file, making both names equal references to the same data.Intermediate
- Hard-Coded CredentialsPasswords, API keys or cryptographic keys embedded directly in source code, scripts or binaries.Foundational
- HardeningReducing a system's attack surface by removing unnecessary functions and applying secure configurations.Foundational
- Hardware Asset Management (HAM)ServiceNow application managing the lifecycle of hardware assets from request and procurement to disposal.Intermediate
- Hardware Debug InterfacePhysical interfaces such as JTAG, SWD and UART used during development that can expose device memory, firmware and consoles.Advanced
- Hardware RAID ControllerA dedicated adapter that implements RAID on its own processor, offloading parity calculation and often providing protected write cache.Intermediate
- Hardware Security KeyPhysical token, such as a USB or NFC key, that performs FIDO2 or U2F authentication.Foundational
- Hardware Security Module (HSM)Tamper-resistant hardware device that generates, stores, and uses cryptographic keys without exposing them.Foundational
- Hardware-Assisted VirtualizationCPU extensions, such as Intel VT-x and AMD-V, that let hypervisors run guests efficiently and securely.Foundational
- Harvest Now, Decrypt Later (HNDL)Strategy of collecting encrypted data today to decrypt it once a quantum computer can break the encryption.Advanced
- Hash CollisionWhen two different inputs produce the same hash digest.Intermediate
- Hash FunctionOne-way function that maps input of any size to a fixed-size digest, used to verify integrity.Foundational
- Hash IndexAn index that maps keys through a hash function to buckets, giving very fast equality lookups but no range support.Advanced
- Hash TotalSum of a non-financial field, such as account numbers, used solely as a batch control.Advanced
- Hash-Based Message Authentication Code (HMAC)MAC construction that combines a cryptographic hash function with a secret key (RFC 2104).Intermediate
- HashiCorp Configuration Language (HCL)The declarative configuration language used by Terraform, Packer, Nomad, and other HashiCorp tools.Foundational
- HashiCorp VaultA secrets management tool that stores static secrets, generates dynamic credentials, and provides encryption as a service.Intermediate
- HAVING ClauseThe clause that filters groups after GROUP BY, typically using aggregate conditions.Foundational
- HCP TerraformHashiCorp's managed service, formerly Terraform Cloud, for running Terraform remotely with shared state, policy, and collaboration.Intermediate
- HDBaseTA standard that carries uncompressed video, audio, Ethernet, control and power over a single category cable up to 100 m.Intermediate
- HDXCitrix's high-definition user experience technologies and remote display protocol (ICA) for virtual apps and desktops.Advanced
- HEADA Git reference to the currently checked-out commit, usually pointing indirectly to the current branch.Intermediate
- HeaderControl information a protocol adds in front of the payload, such as addresses, ports, sequence numbers and flags.Foundational
- Headless ServiceA Kubernetes Service with clusterIP: None that returns individual pod IPs via DNS instead of a single virtual IP.Advanced
- HeadroomThe difference in decibels between a system's nominal operating level and the level at which it clips.Foundational
- Health CheckPeriodic probe a load balancer, DNS service or orchestrator uses to determine whether a target is healthy and should receive traffic.Foundational
- Health Check EndpointAn HTTP endpoint such as /healthz or /ready that reports whether a service is alive and able to serve requests.Foundational
- Health Insurance Portability and Accountability Act (HIPAA)1996 US law whose administrative simplification rules protect the privacy and security of protected health information.Foundational
- Heap-Based Buffer OverflowWriting beyond the bounds of memory allocated on the heap, corrupting adjacent data or allocator metadata.Advanced
- HeartbleedA 2014 OpenSSL vulnerability (CVE-2014-0160) in the TLS heartbeat extension that let attackers read up to 64 KB of server memory per request.Foundational
- Heat MapA matrix visualization in which cell color intensity encodes values, revealing patterns across two dimensions.Foundational
- Heat SinkA passive metal component with fins that draws heat away from a chip and dissipates it into the air.Foundational
- HeijunkaLean technique of leveling production by volume and mix over time.Advanced
- Hello PacketA periodic routing protocol message used to discover neighbors, verify parameters and maintain adjacencies.Foundational
- HelmThe package manager for Kubernetes that templates, installs, upgrades, and rolls back applications packaged as charts.Intermediate
- Helm ChartA Helm package containing Chart.yaml, values.yaml, and Go-templated Kubernetes manifests in a templates directory.Intermediate
- Helm ReleaseA specific installed instance of a Helm chart in a cluster, tracked with a name and revision history.Intermediate
- Helm RepositoryAn HTTP server or OCI registry that hosts packaged Helm charts and an index for discovery.Intermediate
- Help DeskThe front-line IT support function that receives, logs, and resolves user technical issues.Foundational
- Hermetic BuildA build that is fully isolated from the network and host environment, using only declared, pinned inputs.Advanced
- Hertz (Hz)The SI unit of frequency equal to one cycle per second.Foundational
- HeteroscedasticityNon-constant variance of regression residuals across the range of predicted values.Advanced
- HibernationA power state that saves memory contents to disk and powers off completely.Foundational
- Hidden NodeA station that cannot hear another station's transmissions, causing both to transmit and collide at the AP.Intermediate
- Hidden SSIDConfiguring an AP not to include its SSID in beacons, also called SSID cloaking.Foundational
- Hierarchical EscalationRaising an issue to higher management because of impact, SLA risk, or need for authority or resources.Intermediate
- Hierarchical QoS (HQoS)A nested QoS policy where a parent policy shapes aggregate traffic and a child policy queues classes within the shaped rate.Advanced
- Hierarchical RelationshipSpecial lookup relationship available only on the User object, linking a user to another user such as a manager.Intermediate
- High Availability (HA)Design goal of keeping a system operational and accessible for a high percentage of time by eliminating single points of failure.Foundational
- High Availability Stateful Switchover (HA SSO)Controller redundancy where a standby WLC maintains AP and client state for subsecond failover.Advanced
- High Bandwidth Memory (HBM)Stacked DRAM packaged alongside the GPU that provides very high memory bandwidth.Intermediate
- High Dynamic Range (HDR)Video formats that represent a wider range of brightness and color than standard dynamic range, using 10-bit or higher depth.Intermediate
- High Efficiency (HE)The 802.11ax PHY and MAC enhancements.Intermediate
- High Throughput (HT)The PHY and MAC enhancements introduced by 802.11n.Intermediate
- High-bandwidth Digital Content Protection (HDCP)Copy protection that encrypts digital video between a source and display over HDMI, DisplayPort, or DVI.Intermediate
- High-Definition Multimedia Interface (HDMI)A digital audio/video interface standard for TVs, monitors, projectors, and computers.Foundational
- High-Risk AI SystemEU AI Act category of AI systems subject to strict requirements due to significant risk to health, safety, or fundamental rights.Advanced
- High-Water MarkPrinciple that a system's overall impact level equals the highest impact level of any security objective or information type it handles.Intermediate
- High-Water Mark (Incremental Load)The last processed value of a monotonically increasing column, such as a modified timestamp or ID, stored to drive the next incremental extract.Intermediate
- Highlight ReportPRINCE2 time-driven report from the Project Manager to the Project Board on stage progress.Intermediate
- Highly Directional AntennaAn antenna with very narrow beamwidth and high gain, used for long point-to-point links.Intermediate
- HIPAA Breach Notification RuleHIPAA rule requiring notification of individuals, HHS, and sometimes media after a breach of unsecured PHI.Intermediate
- HIPAA De-identificationMethods by which health information is rendered not individually identifiable and no longer PHI: Safe Harbor or Expert Determination.Advanced
- HIPAA Privacy RuleHIPAA rule setting standards for use and disclosure of PHI and individuals' rights over their health information.Intermediate
- HIPAA Security RuleHIPAA rule requiring administrative, physical, and technical safeguards for electronic PHI.Intermediate
- Hire-to-Retire (H2R)HR process covering recruiting, onboarding, employment changes, payroll and offboarding.Intermediate
- HistogramA bar chart showing the frequency distribution of data.Foundational
- HITECH ActHealth Information Technology for Economic and Clinical Health Act of 2009, strengthening HIPAA enforcement and breach notification.Intermediate
- HITRUST CSFCertifiable security and privacy framework harmonizing HIPAA, NIST, ISO, PCI, and other requirements, widely used in healthcare.Intermediate
- Hive Metastore (HMS)A central repository of table definitions, schemas, partitions and file locations used by Hive, Spark and other engines.Advanced
- HMAC-Based One-Time Password (HOTP)OTP algorithm (RFC 4226) that generates codes from a shared secret and an incrementing counter.Intermediate
- HNSWHierarchical Navigable Small World: a graph-based ANN index offering fast, high-recall vector search.Advanced
- Hold Your Own Key (HYOK)Model where encryption keys remain in customer-controlled systems outside the cloud provider at all times.Advanced
- Hold-Down TimerA timer during which a router ignores updates with worse metrics for a route recently marked unreachable.Intermediate
- Home FolderA personal network folder assigned to a user account for storing files.Intermediate
- HomebrewA popular open-source package manager for macOS (and Linux) that installs command-line tools and apps.Intermediate
- Homomorphic EncryptionEncryption that allows computation on ciphertext, producing encrypted results that decrypt to the correct answer.Advanced
- HoneyfileA decoy file, often with an enticing name, that triggers an alert when accessed.Foundational
- HoneynetA network of honeypots that simulates a realistic environment to observe attacker behavior.Foundational
- HoneypotA decoy system designed to attract attackers, detect intrusion attempts and study their techniques.Foundational
- HoneytokenA fake credential, record or data item planted to detect unauthorized access or use.Intermediate
- HooksUser-defined commands that run automatically at points in an agent's lifecycle, such as before or after a tool call.Advanced
- Hop LimitThe 8-bit IPv6 header field, equivalent to the IPv4 TTL, decremented by each router and discarded at zero.Foundational
- Horizontal CablingCabling that runs from the telecommunications room patch panel to work area outlets on the same floor.Foundational
- Horizontal PartitioningSplitting a table by rows into several partitions or tables with the same columns.Intermediate
- Horizontal Pod Autoscaler (HPA)A Kubernetes controller that scales the number of pod replicas based on CPU, memory, or custom metrics.Intermediate
- Horizontal ScalingIncreasing or decreasing capacity by adding or removing instances or nodes; also called scaling out/in.Foundational
- Hoshin KanriLean strategic planning method that aligns organizational goals with execution at all levels.Advanced
- Host Bus Adapter (HBA)An adapter that connects a server to a storage network or devices, most commonly a Fibre Channel HBA or a SAS HBA.Foundational
- Host Header InjectionAbuse of an application's trust in the HTTP Host header to poison links, caches or routing.Advanced
- Host IsolationDisconnecting an endpoint from the network except for the security management channel to contain a threat.Foundational
- Host PoolIn Azure Virtual Desktop, a collection of identical session host VMs that deliver desktops or apps to users.Intermediate
- Host PortionThe trailing bits of an IP address that identify a specific interface within a subnet.Foundational
- Host-Based FirewallSoftware firewall running on an individual endpoint that filters traffic to and from that host.Foundational
- hostname CommandA command that displays the computer's host name on Windows, macOS, and Linux.Foundational
- hostnamectlA systemd utility that views and sets the system hostname and related host metadata.Foundational
- hostPathA Kubernetes volume type that mounts a file or directory from the node's filesystem into a pod.Advanced
- Hosts FileA local text file that maps host names to IP addresses and is checked before DNS on most systems.Foundational
- Hot Aisle/Cold AisleA rack layout in which rows face alternately so equipment intakes share cold aisles and exhausts share hot aisles.Foundational
- Hot DeskingA workspace model where users share desks and log in to a phone or video device to receive their personal settings for the session.Foundational
- Hot PartitionA partition or shard that receives a disproportionate share of traffic, creating a bottleneck while others sit idle.Advanced
- Hot SiteA fully equipped alternate facility with current systems and data that can take over operations almost immediately.Foundational
- Hot SpareAn idle standby drive in a storage array that automatically replaces a failed member and triggers a rebuild.Foundational
- Hot Standby Router Protocol (HSRP)Cisco-proprietary FHRP with one active and one standby router sharing a virtual IP and MAC address.Foundational
- Hot-SwappableA component that can be removed and replaced while the system is running without powering it down.Foundational
- HotfixAn urgent fix applied to production to resolve a critical defect, usually outside the normal release cadence.Foundational
- HotpatchA Windows update method that applies security fixes in memory without requiring a restart.Advanced
- Hotspot 2.0 (HS2.0)Wi-Fi Alliance Passpoint technology enabling automatic, secure roaming onto public Wi-Fi using 802.11u and ANQP.Advanced
- HPE Aruba Networking CentralHPE's cloud (or on-premises) network management platform for Aruba APs, switches, and gateways.Intermediate
- HPE Integrated Lights-Out (iLO)HPE's BMC for ProLiant and Synergy servers offering remote console, virtual media, health monitoring and firmware management.Foundational
- HR CaseRecord in an HR Center of Excellence table that tracks an employee's HR request or inquiry.Foundational
- HR CriteriaConditions based on HR profile attributes used to target HR services, content and lifecycle activities.Intermediate
- HR ProfileRecord holding employee HR-specific data such as employment and personal details, linked to the user record.Intermediate
- HR ServiceConfiguration defining a type of HR request, including its COE, topic, fulfillment, templates and record producer.Intermediate
- HR Service Delivery (HRSD)ServiceNow application suite for delivering employee HR services, cases, knowledge and lifecycle journeys.Foundational
- HSRP Interface TrackingReducing an HSRP router's priority when a tracked interface or object fails so the standby router can take over.Intermediate
- HSRP PreemptionAn HSRP option that lets a router with higher priority take over as active when it comes online.Foundational
- HTML SanitizationRemoving or neutralizing dangerous elements and attributes from user-supplied HTML while keeping safe formatting.Intermediate
- HTTP ActionOmniStudio action that calls a REST endpoint from an OmniScript or Integration Procedure, often via a named credential.Intermediate
- HTTP ListenerHTTP connector source that receives HTTP requests on a configured host, port and path to trigger a flow.Foundational
- HTTP MethodsThe verbs used in HTTP requests, chiefly GET, POST, PUT, PATCH, and DELETE, that map to read, create, replace, partial update, and delete operations.Foundational
- HTTP Request SmugglingExploiting disagreement between front-end and back-end servers about where an HTTP request ends, to hide a second request.Advanced
- HTTP Response SplittingAn attack using CRLF injection to make a server emit what a client or cache interprets as two separate HTTP responses.Advanced
- HTTP Security HeadersResponse headers that enable browser security features such as HSTS, CSP, frame restrictions and MIME sniffing protection.Intermediate
- HTTP Status CodesThree-digit codes in HTTP responses indicating results: 1xx informational, 2xx success, 3xx redirection, 4xx client error, 5xx server error.Foundational
- HTTP Strict Transport Security (HSTS)HTTP response header instructing browsers to connect to a site only over HTTPS for a set time.Intermediate
- HttpCalloutMockInterface implemented in tests to return fake HTTP responses because real callouts are not allowed in tests.Intermediate
- HttpOnly Cookie AttributeA cookie flag that prevents client-side scripts from reading the cookie, reducing session theft via XSS.Foundational
- HubA legacy Layer 1 device that repeats incoming signals out every other port, creating a single shared collision domain.Foundational
- Hub-and-Spoke Network TopologyNetwork design where a central hub network hosts shared services and connectivity, and spoke networks connect only to the hub.Intermediate
- Hub-and-Spoke TopologyA WAN topology in which branch sites (spokes) connect to a central site (hub), and traffic between spokes passes through the hub.Foundational
- Hugging FaceA platform and open-source community hosting models, datasets and libraries such as Transformers.Foundational
- Human EvaluationAssessment of model outputs by human raters, often treated as the gold standard for quality.Foundational
- Human Interface Device (HID)A USB device class for input peripherals such as keyboards, mice, and game controllers.Intermediate
- Human OversightEnsuring humans can monitor, understand, intervene in and override AI system behavior.Foundational
- Human-in-the-Loop (HITL)Design in which humans review, approve or correct AI outputs or actions at defined points.Foundational
- Human-Machine Interface (HMI)The software and screens operators use to view process status and issue commands to an industrial control system.Foundational
- HumanEvalA code-generation benchmark of programming problems scored by whether generated code passes unit tests.Intermediate
- Hunt ListAn ordered list of line groups that a CUCM hunt pilot uses to distribute calls.Intermediate
- Hunt PilotA CUCM pattern that, when dialed, distributes calls to members through a hunt list and line groups.Intermediate
- Hybrid ApproachA combination of predictive and adaptive elements chosen to fit the project and its environment.Intermediate
- Hybrid CloudDeployment model combining two or more distinct clouds, typically private and public, connected to allow data and app portability.Foundational
- Hybrid ControlControl implemented partly as a common control and partly by the individual system.Intermediate
- Hybrid CPU ArchitectureA processor design that combines high-performance cores with power-efficient cores on the same chip.Intermediate
- Hybrid CryptosystemSystem that uses asymmetric cryptography to exchange a symmetric key, then symmetric encryption for bulk data.Foundational
- Hybrid DeploymentDeployment of Mule runtimes on customer-hosted servers registered with and managed from the Anypoint control plane.Intermediate
- Hybrid Key ExchangeCombining a classical and a post-quantum key exchange so the session is secure if either algorithm holds.Advanced
- Hybrid SearchCombining keyword (lexical) and vector (semantic) search results for better retrieval.Intermediate
- Hyper-Threading (HT)Intel's implementation of simultaneous multithreading that presents one physical core as two logical processors.Intermediate
- Hyper-VMicrosoft's Type 1 hypervisor built into Windows Server and Windows client editions.Foundational
- Hyper-V CheckpointHyper-V's point-in-time VM capture; production checkpoints use VSS for application-consistent images, while standard checkpoints include memory state.Intermediate
- Hyper-V Generation 2 VMA Hyper-V VM type using UEFI firmware, Secure Boot, SCSI boot and synthetic devices, versus legacy BIOS-based Generation 1.Intermediate
- Hyper-V ReplicaAsynchronous Hyper-V VM replication from a primary host to a replica host for disaster recovery.Intermediate
- Hyper-V Virtual SwitchA software Layer 2 switch in Hyper-V that connects VMs to each other, the host and external networks.Foundational
- Hyperconverged Infrastructure (HCI)An architecture combining compute, storage and virtualization on standard servers, with software-defined storage pooled across nodes.Foundational
- HyperparameterA configuration value set before training that controls the learning process, rather than being learned from data.Foundational
- Hyperparameter TuningSearching for the hyperparameter values that give the best validation performance.Intermediate
- Hypertext Transfer Protocol (HTTP)The Application-layer request-response protocol for the web, using TCP port 80 by default.Foundational
- Hypertext Transfer Protocol Secure (HTTPS)HTTP carried inside TLS encryption, using TCP port 443 by default (and UDP 443 for HTTP/3).Foundational
- HypervisorSoftware that creates and runs virtual machines by abstracting physical CPU, memory, storage and network resources.Foundational
- Hypothesis TestingA statistical procedure for deciding whether sample evidence is strong enough to reject a null hypothesis about a population.Intermediate
- Hypothesis-Driven DevelopmentApproach that treats product ideas as hypotheses to be tested with measurable outcomes.Intermediate
- Hypothesis-Driven HuntingA threat hunting approach that starts with a testable hypothesis about adversary behavior in the environment.Advanced