Overview
The CIA Triad - Confidentiality, Integrity, and Availability - represents the three fundamental objectives of information security. These core principles guide security control selection, risk assessment, and incident impact evaluation in ISO 27001 and all information security frameworks.
What it means in practice
Every security control you implement protects one or more aspects of the CIA Triad. When assessing risks, you evaluate potential impacts on confidentiality, integrity, and availability. When incidents occur, you measure damage in CIA terms.
Real-world example: A ransomware attack primarily threatens availability (encrypted files become unusable) and integrity (files are modified). A data breach threatens confidentiality (unauthorized disclosure of sensitive information). Controls like encryption protect confidentiality, backups ensure availability, and access controls maintain integrity.
Confidentiality
Definition
Confidentiality ensures information is not disclosed to unauthorized individuals, entities, or processes. Only those with legitimate need and proper authorization can access sensitive information.
What confidentiality protects
Personal data: Customer information, employee records, health data
Business secrets: Trade secrets, strategic plans, pricing models
Financial information: Bank details, payment card data, financial statements
Intellectual property: Source code, patents, proprietary research
Confidential communications: Private emails, legal correspondence
Threats to confidentiality
Data breaches and unauthorized access
Insider threats (malicious or accidental disclosure)
Social engineering and phishing attacks
Weak access controls or authentication
Unencrypted data transmission or storage
Improper disposal of physical documents or media
Third-party data mishandling
ISO 27001 controls protecting confidentiality
A.5.12 - Classification of information: Label data by sensitivity
A.5.15 - Access control: Restrict access to authorized users
A.5.17 - Authentication information: Secure passwords and credentials
A.8.5 - Secure authentication: Multi-factor authentication
A.8.24 - Use of cryptography: Encrypt sensitive data
A.6.6 - Confidentiality agreements: Legal protection through NDAs
A.5.14 - Information transfer: Secure transmission methods
Measuring confidentiality impact
When assessing risk impact on confidentiality, consider:
Legal/regulatory: GDPR fines, regulatory penalties
Reputational: Loss of customer trust, brand damage
Competitive: Disclosure of trade secrets to competitors
Financial: Identity theft, fraud losses, notification costs
GDPR connection: Confidentiality breaches of personal data trigger GDPR notification requirements (72 hours to supervisory authority) and can result in fines up to 4% of global revenue or €20 million, whichever is higher. ISO 27001 confidentiality controls help demonstrate GDPR Article 32 security compliance.
Integrity
Definition
Integrity ensures information remains accurate, complete, and unaltered except by authorized processes. It protects against unauthorized modification, deletion, or corruption of data.
What integrity protects
Data accuracy: Financial records, transaction logs, customer databases
System configurations: Security settings, access rules, network configurations
Source code: Software applications, scripts, automation code
Audit trails: Logs that must remain tamper-proof for compliance
Legal documents: Contracts, agreements, regulatory filings
Threats to integrity
Malware that modifies or corrupts files
Unauthorized changes by insiders or attackers
Software bugs introducing errors
Hardware failures causing data corruption
Human error (accidental deletion or modification)
Man-in-the-middle attacks altering data in transit
Database injection attacks
ISO 27001 controls protecting integrity
A.8.13 - Information backup: Restore data to known good state
A.8.16 - Monitoring activities: Detect unauthorized changes
A.8.24 - Use of cryptography: Hash functions verify data hasn't changed
A.5.3 - Segregation of duties: Prevent unauthorized changes through dual control
A.8.32 - Change management: Control system modifications
A.8.29 - Security testing in development: Prevent code integrity issues
A.5.33 - Protection of records: Maintain record integrity
Measuring integrity impact
When assessing risk impact on integrity, consider:
Operational: Incorrect data leading to wrong business decisions
Financial: Fraudulent transactions, accounting errors
Legal: Contracts or records altered, audit trail compromised
Safety: Critical system configurations changed (healthcare, industrial control)
Integrity verification: Implement checksums, digital signatures, and version control to detect unauthorized changes. Regular integrity checks (file integrity monitoring, database checksums) provide early warning of integrity violations before damage spreads.
Availability
Definition
Availability ensures information and information systems are accessible and usable by authorized users when needed. Systems must be reliable, resilient, and recoverable.
What availability protects
Business operations: Critical applications, customer-facing services
Revenue generation: E-commerce platforms, payment processing
Communication systems: Email, collaboration tools, phone systems
Data access: Databases, file servers, cloud storage
Infrastructure: Networks, servers, workstations
Threats to availability
Distributed Denial of Service (DDoS) attacks
Ransomware encrypting critical data
Hardware failures and capacity exhaustion
Power outages and environmental disasters
Network failures and bandwidth saturation
Software crashes and misconfigurations
Malicious deletion of data or systems
ISO 27001 controls protecting availability
A.8.13 - Information backup: Recovery from data loss
A.5.29 - Information security during disruption: Maintain operations during incidents
A.5.30 - ICT readiness for business continuity: Disaster recovery planning
A.8.6 - Capacity management: Ensure adequate system resources
A.8.14 - Redundancy of information processing facilities: Eliminate single points of failure
A.7.12 - Equipment maintenance: Preventive maintenance to avoid failures
A.8.7 - Protection against malware: Prevent ransomware disruption
Measuring availability impact
When assessing risk impact on availability, consider:
Financial: Revenue loss during downtime, SLA penalties
Operational: Productivity loss, missed deadlines
Reputational: Customer dissatisfaction, service level failures
Legal/regulatory: Compliance violations, contractual breaches
Availability metrics
Recovery Time Objective (RTO): Maximum acceptable downtime
Recovery Point Objective (RPO): Maximum acceptable data loss
Mean Time Between Failures (MTBF): System reliability measure
Mean Time To Repair (MTTR): How quickly you restore service
Uptime percentage: 99.9% (8.76 hours/year downtime), 99.99% (52.6 minutes/year)
Availability costs: High availability is expensive. A 99.9% available system costs much less than 99.999% ("five nines"). Base availability requirements on business impact, not arbitrary targets. Critical revenue systems may need five nines; internal tools might tolerate 99% availability.
Balancing the CIA Triad
Trade-offs between principles
Security controls often involve balancing CIA principles:
Confidentiality vs. Availability: Strong encryption protects confidentiality but may slow system performance or complicate recovery if encryption keys are lost
Integrity vs. Availability: Extensive change control and approval processes protect integrity but may delay urgent system updates needed for availability
Availability vs. Confidentiality: High availability often requires data replication across locations, increasing confidentiality risk from multiple storage points
Context-specific prioritization
Different organizations and information types prioritize CIA differently:
Healthcare: Availability is critical (patient care depends on system access) but confidentiality is legally mandated (HIPAA)
Financial services: Integrity paramount (transaction accuracy) with strong confidentiality and high availability
Public websites: Availability critical (reputational impact), integrity important (prevent defacement), confidentiality less relevant for public data
Research data: Integrity essential (data accuracy), confidentiality varies by sensitivity, availability can tolerate some delay
Risk assessment guidance: When evaluating information security risks, assess impact on each CIA component separately. A single incident might have high confidentiality impact, medium integrity impact, and low availability impact. This granular analysis helps select appropriate controls.
CIA Triad in ISO 27001 processes
Information classification
When classifying assets (A.5.12), consider which CIA principles need protection:
Public: Low CIA requirements
Internal: Medium confidentiality, medium integrity, medium availability
Confidential: High confidentiality, high integrity, variable availability
Critical: High on all three CIA dimensions
Impact assessment in risk analysis
ISO 27001 risk assessments evaluate impact on confidentiality, integrity, and availability separately, then combine or prioritize based on organizational context.
Control selection
Match control types to CIA threats:
Preventive controls: Stop CIA violations before they occur (access controls, encryption)
Detective controls: Identify CIA violations when they happen (monitoring, logging)
Corrective controls: Restore CIA after violations (backups, incident response)
Beyond the CIA Triad
Extended models
Some frameworks add additional security principles:
Authenticity: Verification that data or users are genuine (covered by authentication controls)
Non-repudiation: Proof that actions cannot be denied (audit trails, digital signatures)
Accountability: Traceability of actions to individuals (logging, access controls)
ISO 27001 implicitly addresses these through controls but focuses primarily on CIA.
CIA Triad in incident response
Incident classification
Categorize security incidents by which CIA principle was violated:
Confidentiality incidents: Data breaches, unauthorized access, information leaks
Integrity incidents: Unauthorized modifications, data corruption, defacement
Availability incidents: DDoS attacks, ransomware, system outages
Response prioritization
Severity depends on which CIA principle is affected and its importance to your business. A confidentiality breach of customer PII may be more severe than temporary unavailability of an internal tool.
Related concepts
Risk Assessment - Evaluates threats to CIA
Asset - Items requiring CIA protection
Control - Measures protecting CIA
Information Classification - Categorizing data by CIA requirements
Incident Response - Addressing CIA violations
Getting help
Use ISMS Copilot to assess which CIA principles are most critical for your assets, select controls appropriately, and document CIA impact in your risk assessments.