ISMS Copilot
ISO 27001 Glossary

What is the CIA Triad (Confidentiality, Integrity, Availability)?

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.

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.

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