Secure development life cycle
Security requirements, threat modelling, code review, testing and vulnerability handling are built into development, following practices such as the NIST Secure Software Development Framework.
GCRI · Cybersecurity and Digital Resilience
Safety-critical and secure software
Software and safety-critical systems engineering builds software that must not fail dangerously, in medical devices, vehicles, control systems and infrastructure. In this field it connects security to safety: secure development, verification and the assurance that software behaves as intended under attack and fault.
01Register
Safety-critical and secure software on the record.
Method recordSTEM method
- MethodSoftware and safety-critical systems engineering
- StewardCybersecurity and Digital Resilience
- Applied inCybersecurity and Digital Resilience
- Data3 inputs
- Checks3 validation steps
- Canonical pageSTEM Commons
02Application
What software and safety-critical systems engineering does here.
Software and safety-critical systems engineering develops software whose failure could cause harm, loss of life or major disruption. It applies rigorous processes to control-system, medical, aviation and infrastructure software. In cyber and digital resilience and critical infrastructure, safety-critical software practice limits the chance that a software fault cascades through physical infrastructure. It informs assurance requirements for automated control in interconnected systems. The canonical description is on the STEM Commons.
Safety and security co-assurance
Hazard analysis and threat analysis are performed together so that security measures do not compromise safety functions and vice versa.
Memory-safe language transition
Components most exposed to untrusted input are identified for rewriting in memory-safe languages, which removes a large class of vulnerabilities.
03Geography
Connected activity in Europe.
Night lights, population density and true-colour imagery over Europe, from NASA GIBS. Each layer carries its own date.
The interactive map needs JavaScript; the layer list and sources are below.
Layers 3
Connected activity, for this page
Keyboard, with the map focused
Hold Ctrl or ⌘ and scroll to zoom
Latest available
NASA GIBS / EOSDIS · ASTER GDEM (METI, NASA) · Blue Marble (NASA) · © OpenStreetMap contributors (ODbL) · Natural Earth
Loading the latest NASA imagery.
Drag to move. Ctrl or ⌘ and scroll, pinch or the buttons to zoom; hover for the values under the pointer; reset returns to the region.
Connected activity, framed on Europe.Satellite and model products as NASA publishes them, each with its own date. They are indicators, not assessments of any place.
Data: NASA GIBS · ASTER GDEM · Blue Marble · © OpenStreetMap contributors · Natural Earth · NASA EONET · NASA HLS S30Sources and licences
- We acknowledge the use of imagery provided by services from NASA's Global Imagery Browse Services (GIBS), part of NASA's Earth Science Data and Information System (ESDIS). Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- We acknowledge the use of imagery provided by services from NASA's Global Imagery Browse Services (GIBS), part of NASA's Earth Science Data and Information System (ESDIS). Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- VIIRS Black Marble night-time lights, NASA Goddard Space Flight Center; distributed by the NASA Level-1 and Atmosphere Archive and Distribution System (LAADS DAAC); imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- Center for International Earth Science Information Network (CIESIN), Columbia University. 2018. Gridded Population of the World, Version 4 (GPWv4): Population Density, Revision 11. NASA Socioeconomic Data and Applications Center (SEDAC). Licensed under CC BY 4.0. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). doi:10.7927/H49C6VHW. CC BY 4.0
- VIIRS near-real-time products (flood, land surface temperature, snow cover, corrected reflectance), NASA LANCE; imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- MODIS land products (vegetation indices, gross primary production, land cover), NASA LP DAAC and LANCE; imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- ASTER GDEM is a product of METI and NASA (ASTER Global Digital Elevation Model V003, NASA LP DAAC); imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). Cite as: NASA/METI/AIST/Japan Spacesystems and U.S./Japan ASTER Science Team (2019). ASTER Global Digital Elevation Model V003. doi:10.5067/ASTER/ASTGTM.003. NASA open data
- Made with Natural Earth. Free vector and raster map data @ naturalearthdata.com. Public domain
- © OpenStreetMap contributors (ODbL), via NASA GIBS (coastlines, boundaries, roads and place names). Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). ODbL
- Blue Marble, NASA Earth Observatory; imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- Context on the globe and flat map: coastlines, boundaries, roads and place names from NASA GIBS reference layers (OpenStreetMap data, ODbL, © OpenStreetMap contributors); Blue Marble imagery as an optional base; 3D terrain and the elevation read-out from the ASTER GDEM elevation colour index (5 m to 200 m classes, exaggerated for legibility). Boundaries are drawn as published and imply no position on any territory.
- Live events: NASA Earth Observatory Natural Event Tracker (EONET); events are indicative and keep their original source links.
- Observed (EO): NASA HLS S30 (contains modified Copernicus Sentinel data 2026). We acknowledge the use of imagery provided by services from NASA's Global Imagery Browse Services (GIBS), part of NASA's Earth Science Data and Information System (ESDIS).
- NASA GIBS: We acknowledge the use of imagery provided by services from NASA's Global Imagery Browse Services (GIBS), part of NASA's Earth Science Data and Information System (ESDIS).
- Optional layers (5 sources in the layer list: live, forecast, observed and context) print their provider credit on the map and here when switched on; forecasts are model output and derived indices are estimates.
Layers and dates
- Night-time lights, daily: VIIRS Black Marble (VNP46A2), NASA LAADS DAAC · 12 Oct 2026
- Population density, 2020: Population: CIESIN, Columbia University, Gridded Population of the World v4.11 (2018), NASA SEDAC, CC BY 4.0 · static
- Flood water, 3-day composite: VIIRS Global Flood Product, NASA LANCE · 14 Oct 2026
- True colour: VIIRS NOAA-20 corrected reflectance, NASA LANCE · 13 Oct 2026
- Land cover type (IGBP), yearly: MODIS Terra and Aqua land cover (MCD12Q1), NASA LP DAAC · 2024
- Enhanced vegetation index, rolling 8 days: MODIS Terra EVI, NASA LANCE · 13 Oct 2026
04Data
What the method consumes.
Datasets and records used by software and safety-critical systems engineering on this platform, with the role each plays and the label its values carry. Sources are listed in the source register.
| Data | Role | Label |
|---|---|---|
| Vulnerability reports by root cause | Defect classes | REPORTED |
| Static and dynamic analysis results | Code quality | OBSERVED |
| Hazard and threat analyses | Requirements | DECLARED |
05Monitor
Verification and test.
The screen a team would use to follow this method: its measures, states and decisions. Names are examples and values are illustrative.
Verification and test
Cybersecurity · Safety-critical and secure · Run R-2252
Test campaignGCRI · Cybersecurity and Digital Resilience
Requirements coverage
| REQ-01 safe stop | 32 | 11 | Covered |
| REQ-07 fault detection | 20 | 17 | Gaps |
| REQ-12 timing | 21 | 29 | Covered |
Method card
- Method
- Software and safety-critical systems engineering
- Standard
- traceability matrix
- Reviewer
- independent
- Label
- MODELLED
Findings by severity
06Validation
How results are checked.
Software is verified through reviews, testing to defined coverage criteria and formal proofs where justified. Independent assessment examines the safety case.
| Check | How it is done |
|---|---|
| Independent verification | Safety-critical software is verified by a team independent of development |
| Coverage measures | Tests meet stated structural coverage criteria |
| Vulnerability root cause tracking | Fixed vulnerabilities are classified by cause to improve practice |
Complex software interacting with uncertain environments cannot be exhaustively tested. Updates and third-party components introduce new failure paths.
07Twin and cascade simulator
Model safety-critical and secure software as a system. Run the cascade.
Assembled from the Nexus Standards area profile Cyber and digital resilience law alignment: the hazards it names, the systems and sectors that carry the loss, the controls that dampen it and the data that observe it. Choose the components, pick an initiating hazard and step through the cascade. The Map view places the run on an example geography with open data. Every coupling weight is a stated assumption you can change. A teaching model, not a forecast, an assessment or a certification. To model a place of your own choosing, open the full System Builder.
Hazards
- Dam failure
- Sea-ice loss
- Coastal erosion (set off downstream)
- River flood (set off downstream)
- Flash flood (set off downstream)
- Mass displacement (set off downstream)
- Biodiversity loss (set off downstream)
- Widespread power outage (set off downstream)
- Water supply shortfall (set off downstream)
- Arctic winter sea-ice collapse (set off downstream)
- Polar vortex disruption (set off downstream)
Systems and couplings
Controls
NS-10Policies and clauses (machine-readable obligations: definition, binding, evaluation and enforcement)NS-11Verification and monitoring (evidence, attestations, zero-trust conformance observation)NS-9Contextual UNIs (deployments, instances, programme instances)NRS-X6Cyber and digital security riskNRS-H93Hazard family: Identity, trust and cryptographic failure (NHS-1 cyber.identity)NRS-K31Domain pack profile: Cyber national resilience (DOMAIN-031)NRS-H54Hazard family: Signal and platform disruption (NHS-1 cyber.platform)NRS-H86Hazard family: Telecom and data-centre failure (NHS-1 infra.digital)NRS-H94Hazard family: Systemic cyber events (NHS-1 cyber.systemic-cyber)
Observation
- NIST National Vulnerability Database APIs (listed for reference)
- CISA Known Exploited Vulnerabilities catalogue (listed for reference)
- EUR-Lex Cellar (EU legal acts and delegated acts) (listed for reference)
- Cybersecurity Supply Chain Risk Management
- Legal measures pillar of the Global Cybersecurity Index
Example geography
- North America: 243 hexagonal cells
- Night lights tonight, outages (VIIRS Day/Night Band), NASA GIBS
- Surface water through cloud, 30 m (OPERA DSWx-S1 radar), NASA GIBS
- Rain rate, last half hour (IMERG), NASA GIBS
- Vegetation disturbance alerts, 30 m (OPERA DIST-ALERT), NASA GIBS
08Connections
Topics that rely on this method.
09Methods and evidence
How safety-critical and secure software is modelled, measured and tested.
The model, its assumptions, its data and its uncertainty, in the form a scientist or engineer would check. Structures follow published methods. The values drawn are illustrative, not findings.
System model
The couplings between the systems in safety-critical and secure software: signs of influence, a reinforcing and a balancing loop, and cross-links where stress jumps.
FAIR guiding principles · GO FAIR and FORCE11W3C PROV · World Wide Web ConsortiumGuidance on consistent treatment of uncertainties · IPCCCEOS Analysis Ready Data · Committee on Earth Observation Satellites
10Stewardship
Who maintains the method.
Cybersecurity and Digital Resilience stewards software and safety-critical systems engineering for the Consortium and reviews how it is applied across platforms.
11Process
How the process runs.
Process
Safety-critical and secure software: Risk management process
ISO 31000:2018 sets out an iterative risk management process, from scope, context and criteria through assessment and treatment to monitoring, review and reporting.
01 Frame
- 01Scope, context and criteriaDataset · Service ownerThe frame for the process: the scope, the external and internal context, and the risk criteria. Later steps are read against this frame.
02 Risk assessment
- 04Risk identificationStep · Service ownerThe first part of risk assessment. Risk is usually expressed by risk sources, potential events, their consequences and likelihood.
- 05Risk analysisModel · Service ownerThe second part of risk assessment. It considers consequences and likelihood of the identified risks, with guidelines, not a formula.
- 06Risk evaluationStep · Service ownerThe last part of risk assessment. Results of the analysis are compared with the risk criteria to see where more action is needed.
03 Treatment
- 07Risk treatmentStep · Service ownerTreatment options are selected, then plans are prepared and implemented. Residual risk is documented and goes to monitoring and review.
04 Across the process
- 02Communication and consultationStep · Service ownerCommunication and consultation with stakeholders is its own process element. The standard draws it alongside the others, not in sequence.
- 03Monitoring and reviewStep · Service ownerMonitoring and review take place at every stage. New experience, knowledge and analysis can revise elements, actions and controls.
05 Record and report
- 08Recording and reportingRecord · Service ownerThe process and its outcomes are documented and reported. The standard does not name who receives the report in the clauses read.
Outline of an external standard or method, from its public sources. It describes what the framework says, not a record of any run. It does not show that Nexus or any partner performs, certifies or approves a step. A gate is a step of the method, never a Nexus approval.
12Questions
Questions and answers.
What are the limits of software and safety-critical systems engineering in this field?
Complex software interacting with uncertain environments cannot be exhaustively tested. Updates and third-party components introduce new failure paths.
How are results checked?
Software is verified through reviews, testing to defined coverage criteria and formal proofs where justified. Independent assessment examines the safety case.
Are the values on this page real?
The data names, roles and checks are real descriptions of practice. The canvas shows a design of the method's use, not a run; no result is reported here.
Where else is this method applied?
The canonical method page lists every platform that applies it.
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