CompTIA Glossary
CompTIA certifications cover a wide range of vendor-neutral IT skills, from technical support and networking to cybersecurity, servers, cloud computing, Linux and data. This A–Z glossary explains the terminology learners are likely to encounter across CompTIA courses and exams, alongside practical IT concepts used in everyday technical roles.
A
A+
CompTIA's entry-level professional certification for core IT support skills including hardware, operating systems, networking, security and troubleshooting.
AAA
Authentication, Authorisation and Accounting, a framework for controlling access and recording activity on systems and networks.
Access Control List (ACL)
A set of rules defining which users, systems or network traffic are permitted or denied access to a resource.
Active Directory
Microsoft's directory service for centrally managing users, computers, groups, authentication and policy in Windows environments.
Address
An identifier used to locate a device, service or resource, such as an IP address, MAC address or memory address.
AES
Advanced Encryption Standard, a widely used symmetric encryption algorithm for protecting data.
AI
Artificial Intelligence, the broad field of creating systems capable of performing tasks that normally require human intelligence.
Antivirus
Software designed to detect, block and remove malicious software from endpoints and systems.
API
Application Programming Interface, a defined way for software applications or services to exchange data and commands.
APIPA
Automatic Private IP Addressing, a Windows feature that assigns an address in the 169.254.0.0/16 range when DHCP is unavailable.
Application
Software designed to perform a particular task for a user or another system.
Asset
Any hardware, software, data, service or other resource that has value to an organisation and should be managed or protected.
Attack Surface
The total set of points through which an attacker might try to enter, influence or extract data from a system.
Authentication
The process of proving the identity of a user, device or service.
Authorisation
The process of deciding what an authenticated identity is allowed to access or do.
Availability
The degree to which a system, service or data remains accessible when authorised users need it.
B
Backup
A separate copy of data kept so that information can be restored after deletion, corruption, failure or attack.
Bandwidth
The maximum amount of data a network link can transfer over a period of time.
Bash
A command shell and scripting language widely used on Linux and Unix-like operating systems.
BIOS
Basic Input/Output System, firmware traditionally used to initialise computer hardware and begin the operating-system boot process.
BitLocker
Microsoft's full-disk encryption technology for protecting data on Windows devices.
Bluetooth
A short-range wireless technology used to connect devices such as keyboards, headsets and phones.
Botnet
A collection of compromised devices remotely controlled to carry out activities such as attacks, spam or credential theft.
Brute-Force Attack
An attack that repeatedly tries many password or key combinations until the correct one is found.
Bus
A communication pathway inside a computer used to transfer data between components.
BYOD
Bring Your Own Device, a policy allowing users to access organisational resources from personally owned devices.
C
Cache
Fast temporary storage that keeps frequently used data close to the processor or application to improve performance.
Certificate
A digital credential that binds an identity to a public key and can be used for authentication and encrypted communication.
CIA Triad
Confidentiality, Integrity and Availability, three fundamental objectives used to guide information-security controls.
CIDR
Classless Inter-Domain Routing, a way of representing IP networks with a prefix length such as /24.
Client
A device or software application that requests services or resources from another system known as a server.
CLI
Command-Line Interface, a text-based environment used to run commands and administer systems.
Cloud Computing
The delivery of computing resources such as servers, storage and applications as on-demand services over a network.
Cloud+
A CompTIA certification covering cloud architecture, deployment, operations, security, DevOps fundamentals and troubleshooting.
CloudNetX
An advanced CompTIA certification focused on designing and managing complex hybrid and multi-cloud network environments.
CompTIA
A technology industry organisation known for vendor-neutral professional certifications across IT support, infrastructure, cybersecurity, cloud and data.
Container
A lightweight package containing an application and its dependencies while sharing the host operating-system kernel.
Cookie
Small data stored by a web browser on behalf of a website to maintain sessions, preferences or tracking information.
CPU
Central Processing Unit, the main processor that executes instructions in a computer.
Cryptography
The use of mathematical techniques to protect information through encryption, hashing, digital signatures and related methods.
CVE
Common Vulnerabilities and Exposures, a public naming system that assigns identifiers to disclosed security vulnerabilities.
CVSS
Common Vulnerability Scoring System, a standard method for expressing the severity of a security vulnerability.
CySA+
CompTIA Cybersecurity Analyst, a certification focused on security monitoring, vulnerability management, incident response and defensive analysis.
D
Data+
A CompTIA certification covering practical data analysis, data quality, visualisation, governance and interpretation.
DataAI
A newer CompTIA advanced credential focused on applying artificial intelligence within data and analytics environments.
Database
An organised collection of data designed for efficient storage, retrieval and management.
Data Loss Prevention (DLP)
Controls designed to detect and prevent sensitive data from being exposed, copied or transferred inappropriately.
DataSys+
A CompTIA certification for database administrators covering deployment, maintenance, security, scripting and business continuity.
DDoS
Distributed Denial-of-Service, an attack in which many systems overwhelm a target with traffic or requests.
DHCP
Dynamic Host Configuration Protocol, used to automatically provide clients with IP addresses and other network settings.
Directory Service
A system that stores and organises information about users, devices and resources and supports central authentication or lookup.
Disaster Recovery
Plans, processes and technologies used to restore IT services and data after a major disruption.
Disk
A persistent storage device or logical storage area used to hold operating systems, applications and data.
DMZ
Demilitarised Zone, a network segment used to isolate public-facing services from an internal trusted network.
DNS
Domain Name System, the distributed service that translates names into IP addresses and provides other naming information.
Docker
A widely used platform and toolset for building, packaging and running software containers.
Domain
A defined administrative or naming area, such as an Active Directory domain or an internet DNS domain.
E
EDR
Endpoint Detection and Response, security technology that monitors endpoint activity and helps detect, investigate and contain threats.
Encryption
The conversion of readable information into an unreadable form that requires the correct key to recover.
Endpoint
A user device or system connected to a network, such as a laptop, desktop, server or mobile phone.
Ethernet
The dominant wired local-area networking technology defined by the IEEE 802.3 family of standards.
Event Log
A chronological record of system, application or security events used for administration and troubleshooting.
exFAT
A Microsoft file system commonly used on removable storage where support for large files and broad device compatibility are required.
Exploit
Code or a technique that takes advantage of a vulnerability to cause unintended behaviour or gain access.
F
Fibre Optic
A cabling technology that transmits data as light through glass or plastic fibres and supports high speeds over long distances.
File System
The structure an operating system uses to organise, store and retrieve files on a storage device.
Firewall
A security control that permits or blocks network traffic according to defined rules and, in many cases, connection state.
Firmware
Low-level software stored in hardware devices that controls their basic operation.
Forensics
The disciplined collection, preservation and analysis of digital evidence for investigations.
FQDN
Fully Qualified Domain Name, the complete DNS name of a host or service.
Full Backup
A backup method that copies all selected data each time the backup runs.
G
Gateway
A device or service that connects one network to another and provides a path for traffic leaving the local network.
GPU
Graphics Processing Unit, a processor designed for highly parallel workloads such as graphics, machine learning and scientific computing.
Governance
The policies, responsibilities and controls used to direct how technology, data and security are managed within an organisation.
GPO
Group Policy Object, a collection of Windows settings that can be centrally applied to users and computers in Active Directory.
Group Policy
A Microsoft technology for centrally configuring security, desktop and system settings across managed Windows devices and users.
GUID
Globally Unique Identifier, a large identifier designed to be unique across systems and commonly used by operating systems and applications.
H
Hard Disk Drive (HDD)
A persistent storage device that stores data magnetically on rotating platters.
Hash
A fixed-length value created from input data by a one-way mathematical function and used for integrity checking, password storage and other security purposes.
Help Desk
A support function that receives, records and resolves technical incidents and user requests.
HIDS
Host-Based Intrusion Detection System, software that monitors an individual system for suspicious activity.
HIPS
Host-Based Intrusion Prevention System, endpoint security software designed to detect and actively block suspicious behaviour.
Honeypot
A deliberately exposed or simulated system designed to attract attackers and reveal malicious techniques.
Host
A computer, virtual machine or other device participating in a network.
HTTP
Hypertext Transfer Protocol, the application protocol used for transferring web content.
HTTPS
HTTP protected by TLS encryption to provide confidentiality and server authentication.
Hypervisor
Software or firmware that creates and manages virtual machines on physical hardware.
I
IaaS
Infrastructure as a Service, a cloud model providing virtualised computing, storage and networking resources.
IAM
Identity and Access Management, the policies and technologies used to manage identities, authentication and permissions.
ICMP
Internet Control Message Protocol, used for IP diagnostics and error reporting, including by tools such as ping.
IDS
Intrusion Detection System, technology that monitors activity for signs of attacks or policy violations and generates alerts.
IMAP
Internet Message Access Protocol, used by email clients to access and manage messages stored on a mail server.
Incident
An event that disrupts, threatens or could compromise an IT service, system or security objective.
Incident Response
The organised process of preparing for, detecting, containing, eradicating and recovering from cybersecurity incidents.
Integrity
The assurance that data and systems have not been altered improperly or without authorisation.
Internet of Things (IoT)
Network-connected physical devices such as sensors, cameras and smart equipment that collect or exchange data.
IP
Internet Protocol, the network-layer protocol used to address and route packets between networks.
IP Address
A logical address assigned to a network interface so it can communicate using Internet Protocol.
IPS
Intrusion Prevention System, security technology that detects suspicious network activity and can actively block it.
IPv4
The widely deployed Internet Protocol version using 32-bit addresses.
IPv6
The newer Internet Protocol version using 128-bit addresses and providing a much larger address space than IPv4.
ISO Image
A file containing a complete copy of an optical disc or bootable installation medium.
J
Java
A widely used object-oriented programming language and runtime platform.
Job Scheduler
Software or an operating-system service that automatically runs tasks at specified times or in response to defined conditions.
JSON
JavaScript Object Notation, a lightweight text format widely used for structured data, configuration and APIs.
JWT
JSON Web Token, a compact signed token format commonly used to exchange authentication and authorisation claims between applications.
K
Kerberos
A network authentication protocol using encrypted tickets to authenticate users and services without repeatedly sending passwords.
Kernel
The core part of an operating system that manages hardware, memory, processes and other low-level system functions.
Key
A value used by cryptographic algorithms to encrypt, decrypt, sign or authenticate information.
Keylogger
Software or hardware that records keystrokes, often used maliciously to capture credentials and sensitive information.
Key Management
The processes used to generate, store, distribute, rotate, revoke and protect cryptographic keys.
KVM
Keyboard, Video and Mouse technology that allows one console to control multiple computers or servers.
Kubernetes
An open-source platform for deploying, scaling and managing containerised applications.
L
LAN
Local Area Network, a network covering a limited geographic area such as an office, building or campus.
Latency
The delay between sending data and its arrival or response at another point in a network or system.
LDAP
Lightweight Directory Access Protocol, used to query and manage information held in directory services.
Least Privilege
The security principle of granting users, applications and systems only the minimum access required to perform their tasks.
Linux+
A CompTIA certification validating practical Linux administration, security, scripting, containers and troubleshooting skills.
Load Balancer
A device or service that distributes traffic across multiple servers or resources to improve performance and availability.
Local Account
A user account whose credentials and permissions are stored and managed on an individual computer rather than a central directory.
Log
A chronological record of events, activity or diagnostic information generated by systems and applications.
Logic Bomb
Malicious code designed to activate when a specific condition or time is reached.
LVM
Logical Volume Manager, a Linux storage technology that creates flexible logical storage volumes above physical disks or partitions.
M
MAC Address
A hardware-level address used to identify a network interface on a local Ethernet or wireless network.
Malware
Malicious software designed to disrupt, damage, spy on or gain unauthorised access to systems and data.
MBR
Master Boot Record, an older disk-partitioning and boot structure located at the beginning of a storage device.
MDM
Mobile Device Management, technology used to centrally configure, secure and monitor smartphones, tablets and other managed endpoints.
Memory
Electronic storage used by a computer to hold instructions and data, commonly referring to system RAM.
Metadata
Data describing other data, such as file timestamps, ownership, location, format or document properties.
MFA
Multi-Factor Authentication, requiring two or more different forms of evidence to verify an identity.
MITM Attack
Man-in-the-Middle attack, where an attacker secretly intercepts or alters communication between parties.
Motherboard
The main circuit board connecting a computer's processor, memory, storage interfaces, expansion cards and other components.
MTBF
Mean Time Between Failures, a reliability measure estimating the average operating time between repairable failures.
MTTR
Mean Time to Repair or Mean Time to Restore, a measure of how long it typically takes to recover from a failure.
N
NAC
Network Access Control, technologies that determine whether users and devices may connect to a network and what access they receive.
NAS
Network-Attached Storage, a storage device that provides file access to clients across a network.
NAT
Network Address Translation, the modification of IP addresses as traffic moves between networks.
Network+
A CompTIA certification covering networking concepts, implementation, operations, security and troubleshooting.
Network Segmentation
The division of a network into separate logical or physical areas to improve security, performance and control.
Network Topology
The physical or logical arrangement of network devices and the connections between them.
NIC
Network Interface Card or Controller, hardware that connects a computer or device to a network.
Nmap
An open-source network scanning tool used to discover hosts, ports, services and other network information.
Non-Repudiation
A security property providing evidence that a particular party performed an action and cannot credibly deny it later.
NTFS
New Technology File System, the primary Windows file system supporting permissions, encryption, journaling and large volumes.
NTP
Network Time Protocol, used to synchronise clocks among computers and network devices.
O
OAuth
An authorisation framework that allows applications to obtain limited access to resources without receiving the user's password.
Object Storage
A storage model that manages data as objects with metadata rather than as traditional disk blocks or hierarchical files.
On-Premises
IT infrastructure located and operated within an organisation's own facilities rather than hosted in a public cloud.
Open Source
Software whose source code is made available under a licence that permits inspection, modification and redistribution under defined terms.
Operating System
Core software that manages computer hardware and provides services for applications and users.
Orchestration
The automated coordination of multiple systems, services or tasks to carry out a complete workflow.
OSI Model
A seven-layer conceptual model used to explain and troubleshoot how network communications are structured.
OTP
One-Time Password, a temporary authentication code valid for a single session or short period.
P
PaaS
Platform as a Service, a cloud model providing managed application platforms so developers can deploy software without managing all underlying infrastructure.
Patch
A software update designed to fix defects, improve functionality or close security vulnerabilities.
PenTest+
A CompTIA certification focused on penetration testing, vulnerability assessment, attack techniques, reporting and remediation advice.
Phishing
A social-engineering attack using deceptive messages or websites to trick people into revealing information or taking unsafe actions.
PKI
Public Key Infrastructure, the technologies, policies and services used to issue, manage and validate digital certificates and public keys.
Port
A physical connection on a device or a numerical transport-layer identifier used by TCP and UDP applications.
PowerShell
Microsoft's command shell and scripting environment for system administration and automation.
Privilege Escalation
The process of gaining permissions beyond those originally assigned, whether legitimately or through exploitation.
Project+
A CompTIA certification covering practical project-management concepts, communication, documentation, change and delivery.
Protocol
A defined set of rules and message formats that enables devices or software to communicate.
Proxy Server
An intermediary server that forwards requests between clients and other services, often adding filtering, caching, privacy or security controls.
Public Key
The shareable half of an asymmetric cryptographic key pair, used for encryption or signature verification depending on the application.
Q
QoS
Quality of Service, techniques used to prioritise or manage network traffic so important applications receive appropriate treatment.
QR Phishing
A phishing technique, sometimes called quishing, that uses a malicious QR code to direct a victim to a deceptive website or action.
Query
A request used to retrieve, filter or manipulate information in a database, search system or other data source.
Queue
A temporary holding structure in which tasks, messages or data wait to be processed.
R
RADIUS
Remote Authentication Dial-In User Service, a protocol used for centralised network authentication, authorisation and accounting.
RAID
Redundant Array of Independent Disks, techniques for combining multiple disks to improve performance, capacity or fault tolerance.
RAM
Random Access Memory, fast temporary memory used by running operating systems and applications.
Ransomware
Malware that encrypts, steals or otherwise blocks access to data and demands payment or another concession.
RBAC
Role-Based Access Control, a permissions model that assigns access according to a user's job role or function.
RDP
Remote Desktop Protocol, Microsoft's protocol for remotely accessing a Windows graphical desktop.
Recovery Point Objective (RPO)
The maximum acceptable amount of data loss measured as a period of time before an outage.
Recovery Time Objective (RTO)
The target time within which a service should be restored after a disruption.
Registry
A hierarchical Windows database containing operating-system, application, hardware and user configuration settings.
Risk Assessment
The process of identifying threats and vulnerabilities, estimating likelihood and impact, and determining appropriate treatment.
Rootkit
Malware designed to maintain privileged access while hiding its presence from users or security tools.
Router
A network device that forwards IP packets between different networks.
RSA
A widely known asymmetric cryptographic algorithm used in digital signatures, certificates and key-related security functions.
S
SaaS
Software as a Service, a cloud model where complete applications are delivered to users over a network.
Sandbox
An isolated environment used to run or analyse software while limiting its ability to affect production systems.
SecAI+
A newer CompTIA certification focused on applying artificial intelligence to security operations while understanding associated AI risks and controls.
Security+
CompTIA's widely recognised certification covering foundational cybersecurity concepts, architecture, operations, identity, risk and incident response.
SecurityX
CompTIA's expert-level cybersecurity certification, formerly known as CASP+, focused on security architecture, engineering and governance.
Server+
A CompTIA certification covering server hardware, administration, security, disaster recovery and troubleshooting.
SIEM
Security Information and Event Management, technology that centralises security logs and analyses events for suspicious activity.
Smishing
Phishing carried out through SMS or other mobile text messages.
SMTP
Simple Mail Transfer Protocol, used for sending and relaying email messages.
SNMP
Simple Network Management Protocol, used to monitor and manage network devices and other systems.
SOAR
Security Orchestration, Automation and Response, technology that coordinates security tools and automates incident-handling workflows.
Social Engineering
The manipulation of people into revealing information or performing actions that compromise security.
SQL
Structured Query Language, widely used to define, query and modify data in relational databases.
SSD
Solid-State Drive, persistent storage using flash memory rather than moving mechanical parts.
SSH
Secure Shell, an encrypted protocol used for remote command-line administration and secure tunnelling.
SSL
Secure Sockets Layer, an older cryptographic protocol now replaced by TLS but still commonly referenced when discussing encrypted web traffic.
SSO
Single Sign-On, an authentication approach that lets a user access multiple applications after signing in once to a trusted identity provider.
Subnet
A logical subdivision of an IP network containing a defined range of addresses.
Supply Chain Attack
An attack that compromises a trusted supplier, software dependency or service in order to reach downstream targets.
Switch
A network device that forwards Ethernet frames between connected devices, primarily using MAC addresses.
Symmetric Encryption
Encryption in which the same secret key is used for both encryption and decryption.
T
TCP
Transmission Control Protocol, a connection-oriented transport protocol providing reliable, ordered data delivery.
TCP/IP
The suite of networking protocols underpinning the internet and most modern enterprise networks.
Tech+
CompTIA's foundational certification for people beginning their IT learning, covering technology concepts, infrastructure, applications, security and basic troubleshooting.
Threat
Anything capable of causing harm to a system, service, organisation or information asset.
TLS
Transport Layer Security, the modern cryptographic protocol used to protect application communications such as HTTPS.
Token
A value used to represent an authenticated session, authorisation claim, device or other security context.
TOTP
Time-Based One-Time Password, a temporary authentication code generated from a shared secret and the current time.
TPM
Trusted Platform Module, a hardware security component used to protect cryptographic keys and support device integrity features.
Traceroute
A diagnostic tool that shows the sequence of Layer 3 hops a packet takes towards a destination.
Trojan
Malicious software disguised as legitimate or desirable software to persuade a user to install or run it.
Type 1 Hypervisor
A hypervisor that runs directly on physical hardware rather than on top of a general-purpose host operating system.
Type 2 Hypervisor
A hypervisor that runs as an application on a host operating system.
U
UDP
User Datagram Protocol, a connectionless transport protocol with low overhead and no built-in delivery guarantee.
UEFI
Unified Extensible Firmware Interface, the modern firmware standard that has largely replaced traditional PC BIOS.
UPS
Uninterruptible Power Supply, a device that provides temporary battery power and power conditioning during electrical problems.
Update
A software or firmware release providing fixes, security patches, features or compatibility improvements.
URI
Uniform Resource Identifier, a string that identifies a resource, commonly used in web technologies and APIs.
USB
Universal Serial Bus, a widely used standard for connecting peripherals, storage and other devices.
User Account
An identity representing a person or service and containing associated authentication and access settings.
UTM
Unified Threat Management, a security appliance or platform combining multiple controls such as firewalling, malware protection and filtering.
V
VDI
Virtual Desktop Infrastructure, technology that hosts desktop environments centrally and delivers them remotely to users.
Virtual Machine (VM)
A software-defined computer with virtual CPU, memory, storage and networking running on a hypervisor.
Virtualisation
The creation of software-based versions of computing resources such as servers, networks, storage or desktops.
Virus
Malware that attaches itself to files or programs and replicates when the infected content is executed.
Vishing
Voice phishing, where attackers use telephone or voice communication to manipulate victims into revealing information or taking unsafe actions.
VLAN
Virtual Local Area Network, a logical Layer 2 network used to separate broadcast domains on shared switching infrastructure.
VPN
Virtual Private Network, an encrypted or logically isolated connection across another network such as the internet.
Vulnerability
A weakness in software, hardware, configuration, process or behaviour that could be exploited by a threat.
W
WAF
Web Application Firewall, a security control designed to inspect and filter HTTP and HTTPS traffic to web applications.
WAN
Wide Area Network, a network connecting geographically separated locations.
Web Proxy
An intermediary service that forwards web requests and can provide filtering, caching, access control or privacy.
Wi-Fi
A family of wireless LAN technologies based on IEEE 802.11 standards.
Windows Registry
A hierarchical database storing Windows operating-system, hardware, application and user configuration.
Worm
Malware capable of self-replicating and spreading between systems without needing to attach itself to another program.
WPA2
A widely used Wi-Fi security standard based on strong AES encryption.
WPA3
A newer Wi-Fi security standard providing stronger authentication and protection than WPA2.
X
X.509 Certificate
A standard digital certificate format used in public key infrastructure and encrypted network communications.
XML
Extensible Markup Language, a structured text format used by applications, configuration files and web services.
XSS
Cross-Site Scripting, a web vulnerability that allows untrusted script content to execute in a victim's browser.
Y
YAML
A human-readable structured data format commonly used for configuration, infrastructure automation and application deployment files.
Yottabyte
A decimal data-size unit equal to 10 to the power of 24 bytes.
Z
Zero-Day Vulnerability
A vulnerability for which defenders have had no prior opportunity to deploy a fix before exploitation or disclosure.
Zero Trust
A security approach that requires continual verification of identities, devices and access context rather than trusting users based solely on network location.
Zombie Computer
A compromised device remotely controlled by an attacker, often as part of a botnet.
Zone
A logical or physical area used to group systems with similar security, network or administrative requirements.
Explore related CompTIA training and resources
Explore our CompTIA training courses and CompTIA certification pathways. You may also find our Cyber Security Glossary, Cloud Computing Glossary and Data Centre Glossary useful. You can also browse our full course catalogue.
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