CompTIA IT Acronyms & Glossary

CompTIA loves acronyms. This glossary collects the ones you are most likely to meet on the A+, Network+, and Security+ exams, each with a plain-English definition. For exam-specific lists see the Network+ acronyms page.

Current exam references: A+ 220-1101 / 220-1102, Network+ N10-009, and Security+ SY0-701.

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ACL: Access Control List — rules that permit or deny network/file access.
AES: Advanced Encryption Standard — symmetric block cipher (128/192/256-bit).
AP: Access Point — device that connects wireless clients to a wired network.
APIPA: Automatic Private IP Addressing — 169.254.x.x address when DHCP fails.
ARP: Address Resolution Protocol — maps IP addresses to MAC addresses.
BIOS: Basic Input/Output System — firmware that starts hardware at boot.
BYOD: Bring Your Own Device — policy allowing personal devices at work.
CIA: Confidentiality, Integrity, Availability — the core security triad.
CIDR: Classless Inter-Domain Routing — flexible subnet prefix notation (e.g. /24).
DHCP: Dynamic Host Configuration Protocol — auto-assigns IP configuration.
DLP: Data Loss Prevention — controls that stop sensitive data exfiltration.
DNS: Domain Name System — resolves hostnames to IP addresses (port 53).
DoS: Denial of Service — attack that overwhelms a resource to make it unavailable.
EFS: Encrypting File System — file-level encryption in Windows NTFS.
FTP: File Transfer Protocol — transfers files (ports 20/21).
GPO: Group Policy Object — Windows configuration applied to users/computers.
HTTPS: Hypertext Transfer Protocol Secure — encrypted web traffic (port 443).
IDS: Intrusion Detection System — monitors and alerts on suspicious activity.
IPS: Intrusion Prevention System — detects and actively blocks threats.
LDAP: Lightweight Directory Access Protocol — directory queries (port 389).
MAC: Media Access Control — unique 48-bit hardware address on a NIC.
MFA: Multi-Factor Authentication — two or more independent authentication factors.
NAT: Network Address Translation — maps private IPs to a public IP.
NIC: Network Interface Card — hardware that connects a host to the network.
OSI: Open Systems Interconnection — the 7-layer networking reference model.
PKI: Public Key Infrastructure — framework of keys and certificates.
RADIUS: Remote Authentication Dial-In User Service — centralized AAA.
RAID: Redundant Array of Independent Disks — disk redundancy/performance.
RDP: Remote Desktop Protocol — remote GUI access to Windows (port 3389).
SIEM: Security Information and Event Management — log aggregation and correlation.
SMTP: Simple Mail Transfer Protocol — sends email (port 25).
SNMP: Simple Network Management Protocol — monitors network devices (161/162).
SSD: Solid State Drive — flash-based storage with no moving parts.
SSH: Secure Shell — encrypted remote command-line access (port 22).
SSID: Service Set Identifier — the name of a wireless network.
SSO: Single Sign-On — one set of credentials for multiple systems.
TCP: Transmission Control Protocol — reliable, connection-oriented transport.
TLS: Transport Layer Security — modern encryption protocol, successor to SSL.
TPM: Trusted Platform Module — chip that stores keys for full-disk encryption.
UDP: User Datagram Protocol — fast, connectionless transport.
UEFI: Unified Extensible Firmware Interface — modern BIOS replacement.
UPS: Uninterruptible Power Supply — battery backup for clean shutdowns.
VLAN: Virtual LAN — logically segments a switch into separate networks.
VPN: Virtual Private Network — encrypted tunnel over a public network.
WPA: Wi-Fi Protected Access — WPA is legacy; use WPA2 or WPA3, with WPA3 the current standard.
AAA: Authentication, Authorization, and Accounting — framework for controlling and tracking access.
CAT: Category — performance rating for twisted-pair Ethernet cabling, such as Cat 5e, Cat 6, or Cat 6A.
DDoS: Distributed Denial of Service — availability attack launched from many systems at once.
EAP: Extensible Authentication Protocol — framework used for network access authentication, including 802.1X.
GDPR: General Data Protection Regulation — European Union privacy law governing personal data.
HTTP: Hypertext Transfer Protocol — web application protocol, typically using port 80 without TLS.
ICMP: Internet Control Message Protocol — carries diagnostic and error messages, including ping.
IMAP: Internet Message Access Protocol — email retrieval protocol that keeps messages synchronized with the server.
IoT: Internet of Things — network-connected devices such as sensors, cameras, and appliances.
IP: Internet Protocol — network-layer protocol that addresses and routes packets between networks.
ISP: Internet Service Provider — organization that provides Internet connectivity.
MDM: Mobile Device Management — centralized management and security controls for mobile devices.
NFC: Near Field Communication — short-range wireless technology used for contactless communication.
OS: Operating System — software that manages hardware resources and provides services to applications.
PCI DSS: Payment Card Industry Data Security Standard — security requirements for organizations that handle cardholder data.
PII: Personally Identifiable Information — data that can identify, contact, or locate an individual.
PoE: Power over Ethernet — supplies electrical power and network data through Ethernet cabling.
POP3: Post Office Protocol version 3 — email retrieval protocol that commonly downloads messages to a client.
PXE: Preboot Execution Environment — standard for booting a computer from a network before an operating system is installed.
RAM: Random Access Memory — volatile working memory used by active programs and the operating system.
ROM: Read-Only Memory — nonvolatile storage that retains firmware or other data without power.
SATA: Serial Advanced Technology Attachment — interface used to connect storage devices such as HDDs and SSDs.
SFTP: SSH File Transfer Protocol — secure file transfer protocol that runs over SSH.
SLA: Service Level Agreement — documented service expectations, responsibilities, and performance targets.
SQLi: SQL Injection — attack that manipulates database queries through unsafely handled input.
SSL: Secure Sockets Layer — deprecated legacy encryption protocol replaced by TLS.
USB: Universal Serial Bus — standard for connecting peripherals and delivering power and data.
VoIP: Voice over Internet Protocol — technology that delivers voice calls over IP networks.
WAP: Wireless Access Point — device that provides wireless clients with access to a wired network.
WLAN: Wireless Local Area Network — local network that uses Wi-Fi or another wireless technology.
XSS: Cross-Site Scripting — attack that injects untrusted script into a web page viewed by other users.
ZTNA: Zero Trust Network Access — access model that verifies users and devices before granting application access.

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