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.
- 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 — wireless security (WPA2/WPA3 current).
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