Secure Software Lifecycle (SSLM)

This document describes how a secure software lifecycle is implemented in regulated, vendor-hosted environments in a way that produces continuous, auditable evidence without slowing delivery.

The focus is on practical execution, ownership, and traceability.

Why SSLM matters in regulated environments

Modern regulations and customer security requirements increasingly expect organisations to demonstrate:

  • Secure development practices

  • Control over third-party and open-source components

  • Continuous vulnerability management

  • Evidence that security controls are applied consistently

SSLM provides the technical foundation for meeting these expectations across ISO 27001, NIS2, and the Cyber Resilience Act (CRA).

Core principles

A compliant SSLM implementation follows these principles:

  • Shift left, but verify continuously

  • Automate wherever possible

  • Separate policy from enforcement

  • Make evidence a by-product of delivery

  • Keep ownership with engineering teams

Lifecycle stages

The secure software lifecycle is implemented across the following stages.

1. Design & planning

Security begins before code is written.

Key practices include:

  • Threat modelling aligned to product context

  • Architecture decisions documented and versioned

  • Security requirements linked to backlog items

  • Clear definition of control ownership

Outputs:

  • Architecture decision records (ADRs)

  • Threat models

  • Security requirements mapped to features

2. Build & dependency management

During development and build:

  • Source code is continuously scanned

  • Open-source dependencies are inventoried

  • Licensing constraints are evaluated

Typical controls:

  • Static Application Security Testing (SAST)

  • Software Composition Analysis (SCA)

  • Automated SBOM generation

Outputs:

  • Scan results linked to commits

  • SBOM artefacts per build

  • Dependency and license reports

3. Pipeline enforcement

CI/CD pipelines enforce security controls consistently.

Controls typically include:

  • Policy-as-code gates

  • Minimum security baselines

  • Environment separation (build, test, production)

Pipelines are designed so that:

  • Failures are actionable

  • Exceptions are traceable

  • Overrides require approval

Outputs:

  • Pipeline execution logs

  • Policy evaluation results

  • Approval records

4. Testing & verification

Beyond static checks, runtime and configuration issues are validated.

Common practices:

  • Dynamic Application Security Testing (DAST)

  • Infrastructure-as-Code (IaC) scanning

  • Container image scanning

Outputs:

  • Test results tied to pipeline runs

  • Identified issues with severity and context

  • Evidence of remediation or risk acceptance

5. Release & deployment

Before release:

  • Artefact integrity is verified

  • Provenance is established

  • Release approvals are recorded

Typical mechanisms:

  • Artifact signing

  • Attestation of build provenance

  • Environment-specific deployment approvals

Outputs:

  • Signed artefacts

  • Deployment records

  • Release approval evidence

6. Operate & maintain

After deployment, security continues.

Practices include:

  • Continuous vulnerability monitoring

  • Patch and remediation workflows

  • Change tracking for deployed systems

Outputs:

  • Vulnerability lifecycle records

  • Change management evidence

  • Monitoring and alerting data

Evidence-by-design

A key objective of SSLM is that evidence is generated automatically.

Rather than preparing evidence manually for audits or tenders, SSLM produces:

  • Timestamped artefacts

  • Immutable logs

  • Traceability across requirements, code, and deployment

This enables:

  • Faster audits

  • Predictable tender responses

  • Reduced engineering disruption

Alignment with regulations

SSLM directly supports:

  • ISO/IEC 27001 (A.8, A.12, A.14, A.18)

  • NIS2 risk management and supply-chain controls

  • CRA secure development and vulnerability handling requirements

  • Customer security questionnaires and assurance requests

Detailed mappings are covered in the Compliance Mapping section.

What SSLM does not solve alone

SSLM is necessary, but not sufficient on its own.

It must be complemented by:

  • Cloud security foundations

  • Clear vulnerability ownership models

  • SOC and incident response capabilities

  • Governance and reporting structures

These are covered in adjacent solution documents.

Next steps

To continue, review:

  • Vulnerability Lifecycle for how issues are handled end-to-end

  • Cloud Security Foundations for infrastructure-level controls

  • Evidence Library for how SSLM outputs are reused in audits and tenders