Software Security Requirements

Created: 2025-12-04 15:45
#note

Software security requirements define the security properties, controls, and constraints that a system must satisfy. They are an essential component of the Secure SDLC requirements phase and serve as the foundation for building secure systems from the ground up.

Overview

Security requirements differ from functional requirements in that they specify what the system should prevent or withstand, rather than what it should do. These requirements guide architectural decisions, implementation practices, and testing strategies throughout the development lifecycle.

Types of Security Requirements

1. Confidentiality Requirements

Ensure that sensitive information is accessible only to authorized entities:

Data encryption requirements (at rest and in transit)
Access control policies
Authentication mechanisms
Data classification and handling procedures

2. Integrity Requirements

Guarantee that data and systems remain accurate and unaltered:

Data validation and sanitization
Digital signatures and checksums
Audit logging
Version control and change tracking

3. Availability Requirements

Ensure that systems and data remain accessible to authorized users:

Uptime and reliability targets
Disaster recovery and business continuity
Protection against denial-of-service attacks
Redundancy and failover mechanisms

4. Authentication Requirements

Verify the identity of users and systems:

Multi-factor authentication (MFA)
Password policies and strength requirements
Session management
Single sign-on (SSO) integration

5. Authorization Requirements

Control what authenticated entities can access and modify:

Role-based access control (RBAC)
Attribute-based access control (ABAC)
Principle of least privilege
Segregation of duties

6. Non-Repudiation Requirements

Ensure that actions cannot be denied by their originators:

Digital signatures
Audit trails and logging
Timestamping

Sources of Security Requirements

Regulatory Compliance: GDPR, HIPAA, PCI-DSS, SOC 2, etc.
Industry Standards: ISO 27001, NIST frameworks, OWASP guidelines
Threat Modeling: Identified threats and attack vectors
Business Requirements: Organizational security policies and risk appetite
Previous Incidents: Lessons learned from past security breaches
Supply Chain Security: Requirements from vendors and third-party components

Defining Effective Security Requirements

Good security requirements should be:

Specific: Clearly defined and unambiguous
Measurable: Can be tested and verified
Achievable: Technically and economically feasible
Relevant: Address actual security risks
Testable: Can be validated through security testing

Examples

Poor requirement: "The system must be secure"

Good requirements:

"All user passwords must be hashed using bcrypt with a minimum cost factor of 12"
"All API communications must use TLS 1.3 or higher"
"Users must authenticate using MFA for access to sensitive data"
"The system must log all administrative actions with timestamps and user identifiers"
"Session tokens must expire after 30 minutes of inactivity"

Integration with Development

Security requirements should be:

Documented in the same format as functional requirements
Prioritized based on risk assessment
Traceable throughout the development lifecycle
Validated through Static Code Analysis, Penetration Testing, and security reviews
Included in acceptance criteria and definition of done

Common Pitfalls

Vague Requirements: "System should be secure" or "Use industry best practices"
Conflicting Requirements: Security requirements that contradict usability or performance goals
Over-Engineering: Implementing excessive security controls that don't address actual risks
Under-Specification: Missing critical security requirements due to incomplete Threat Modeling
Ignoring Dependencies: Not considering security requirements of third-party dependencies