IT Acronyms

A-Z glossary of acronyms commonly seen on CompTIA and other IT certification exams.

Showing 88 of 88 acronyms

Acronym	Full Name	Context
AAA	Authentication, Authorization, and Accounting	Security framework (RADIUS, TACACS+)
ACL	Access Control List	Network/file permission rules
AES	Advanced Encryption Standard	Symmetric block cipher (128/192/256-bit)
AP	Access Point	Wireless networking device
API	Application Programming Interface	Software integration interface
ARP	Address Resolution Protocol	Maps IP addresses to MAC addresses
BGP	Border Gateway Protocol	Internet routing between autonomous systems
BIOS	Basic Input/Output System	Legacy firmware interface
CA	Certificate Authority	Issues and manages digital certificates
CIDR	Classless Inter-Domain Routing	IP addressing/subnetting notation (/24)
CIA	Confidentiality, Integrity, Availability	Core security triad
CLI	Command-Line Interface	Text-based system interface
CPU	Central Processing Unit	Main processor in a computer
CRL	Certificate Revocation List	List of revoked digital certificates
DDoS	Distributed Denial of Service	Attack using multiple sources
DHCP	Dynamic Host Configuration Protocol	Automatic IP address assignment
DLP	Data Loss Prevention	Tools to prevent data exfiltration
DMZ	Demilitarized Zone	Network segment between internal and external
DNS	Domain Name System	Resolves domain names to IP addresses
DoS	Denial of Service	Attack to disrupt availability
EAP	Extensible Authentication Protocol	Framework for network authentication
FTP	File Transfer Protocol	File transfer (ports 20/21)
GPO	Group Policy Object	Windows policy management
GUI	Graphical User Interface	Visual system interface
HIDS	Host-based Intrusion Detection System	Monitors a single host for threats
HTTP	Hypertext Transfer Protocol	Web traffic (port 80)
HTTPS	Hypertext Transfer Protocol Secure	Encrypted web traffic (port 443)
IaaS	Infrastructure as a Service	Cloud model (VMs, storage, networking)
ICMP	Internet Control Message Protocol	Network diagnostics (ping, traceroute)
IDS	Intrusion Detection System	Monitors and alerts on threats
IMAP	Internet Message Access Protocol	Email retrieval (port 143/993)
IoT	Internet of Things	Network-connected physical devices
IP	Internet Protocol	Network layer addressing (IPv4/IPv6)
IPS	Intrusion Prevention System	Monitors and blocks threats
IPSec	Internet Protocol Security	Encrypted IP communication (VPN)
KDC	Key Distribution Center	Kerberos authentication server
LDAP	Lightweight Directory Access Protocol	Directory services (port 389/636)
MAC	Media Access Control	Hardware address (Layer 2)
MFA	Multi-Factor Authentication	Two or more authentication factors
MITM	Man-in-the-Middle	Attack intercepting communications
MTU	Maximum Transmission Unit	Largest packet size for a network
NAC	Network Access Control	Endpoint compliance enforcement
NAT	Network Address Translation	Maps private IPs to public IPs
NDA	Non-Disclosure Agreement	Legal confidentiality agreement
NIDS	Network-based Intrusion Detection System	Monitors network traffic for threats
NTP	Network Time Protocol	Clock synchronization (port 123)
OCSP	Online Certificate Status Protocol	Real-time certificate validation
OSI	Open Systems Interconnection	7-layer networking reference model
OSPF	Open Shortest Path First	Link-state routing protocol
OU	Organizational Unit	Active Directory container
PaaS	Platform as a Service	Cloud model (app hosting)
PAM	Privileged Access Management	Controls admin/root access
PII	Personally Identifiable Information	Data that identifies an individual
PKI	Public Key Infrastructure	Certificate-based trust framework
POP3	Post Office Protocol v3	Email retrieval (port 110/995)
PSK	Pre-Shared Key	Shared secret for authentication
RAID	Redundant Array of Independent Disks	Disk redundancy/performance (0, 1, 5, 6, 10)
RDP	Remote Desktop Protocol	Windows remote access (port 3389)
RPO	Recovery Point Objective	Max acceptable data loss (time)
RTO	Recovery Time Objective	Max acceptable downtime
SaaS	Software as a Service	Cloud model (hosted applications)
SCP	Secure Copy Protocol	Encrypted file transfer over SSH
SFTP	SSH File Transfer Protocol	Secure file transfer (port 22)
SIEM	Security Information and Event Management	Log aggregation and analysis platform
SLA	Service Level Agreement	Contracted uptime/performance guarantees
SMTP	Simple Mail Transfer Protocol	Email sending (port 25/587)
SNMP	Simple Network Management Protocol	Network device monitoring (port 161/162)
SOAR	Security Orchestration, Automation, and Response	Automated incident response platform
SOC	Security Operations Center	Team/facility for monitoring security
SSH	Secure Shell	Encrypted remote access (port 22)
SSID	Service Set Identifier	Wi-Fi network name
SSL	Secure Sockets Layer	Legacy encryption (replaced by TLS)
STP	Spanning Tree Protocol	Prevents Layer 2 switching loops
TCP	Transmission Control Protocol	Reliable, connection-oriented transport
TFTP	Trivial File Transfer Protocol	Simple file transfer (port 69, UDP)
TLS	Transport Layer Security	Encryption for HTTPS, email, VPN
TPM	Trusted Platform Module	Hardware security chip
UDP	User Datagram Protocol	Fast, connectionless transport
UEFI	Unified Extensible Firmware Interface	Modern BIOS replacement
UPS	Uninterruptible Power Supply	Battery backup for power outages
UTM	Unified Threat Management	All-in-one security appliance
VLAN	Virtual Local Area Network	Logical network segmentation
VM	Virtual Machine	Software-emulated computer
VPN	Virtual Private Network	Encrypted tunnel over public network
WAF	Web Application Firewall	Protects web apps (Layer 7)
WPA	Wi-Fi Protected Access	Wireless security (WPA2/WPA3 current)
XSS	Cross-Site Scripting	Web vulnerability — injected scripts
ZTNA	Zero Trust Network Access	Never trust, always verify model