Capella Cybersecurity Viewpoint

The intent of this viewpoint is to support effective co-engineering between systems and cybersecurity engineering teams when performing the following tasks:

Cybersecurity Projects

To create a project with the Cybersecurity viewpoint activated automatically, select File->New->Cybersecurity Project from the application menu.

Concepts

Cybersecurity Specific Properties of Model Elements can be seen in the Cybersecurity tab of the Properties View. This section lists the most important concepts and their properties.

Actor

An Actor is involved in Threats and allocates one or more Functions.

Threat Source Someone or something that could affect the product (ref: 87210649-DDQ-GRP-EN - Cyber Security For Architects Guide). Yes/No
Threat Source Profile Type of threat source. 1 to 5
Trusted Ability to be relied on as honest or truthful. Threat Source = Yes => Trusted = false. Yes/No
Rationale Rationale on the cybersecurity attributes. The trustworthiness of an Actor is absolute, it does not depend on the Threat that the Actor is involved in, or a given security property. Details on this aspect and others can be exposed in this Rationale field. Text

Threat

A situation that is unwanted by the stakeholders and that is to be avoided. Threat is an abstract concept that is concretized by the following kinds of attacks:

Eavesdropping Secretly listening to the private conversation of others without their consent.
Theft and data alteration Stealing, leaking data, modifying data, erasing data, attack against traceability or against rogue action detection.
Denial of Service DoS attacks make a machine, a service or a network resource unavailable to its intended users.
Intrusion Entering an information system without permission.
Tampering Tampering attacks refer to many forms of sabotage (intentional modification of the information system in a way that makes them harmful).

Threats are applied to Primary Assets. A Threat has the following additional attributes:

Level Priority level given to a Threat at a given stage of design process. It can be motivated by cybersecurity risk analysis; e.g. may be an indication of the likelihood of threat scenarios and the impact of the feared event associated to the threat. 1 to 5
Rationale Rationale on the cybersecurity attributes. Text

Primary Asset

Information, activity, process or functionality that is valuable for the customer and then needs to be protected (ref: 87210649-DDQ-GRP-EN - Cyber Security For Architects Guide). The Cybersecurity Viewpoint distinguishes between:

Functional Primary Asset Activity, process or functionality that is valuable for the customer and then needs to be protected. Functions
Information Primary Asset Information that is valuable for the customer and then needs to be protected. Exchange Items

The attributes of a Primary Asset are its corresponding Security Needs, i.e. the characteristics that can be compromised / affected by a threat (based on ref: 87210649-DDQ-GRP-EN - Cyber Security For Architects Guide) and their sensitivity levels. The following characteristics are considered here:

An asset can define a value between 0 and 3 for each of these attributes. Project/Product teams shall define the equivalences between these sensitivity levels and those specific to their standards framework.

Primary Assets are threatened by Threats.

Function

Action, operation or service performed by the system, or by an actor interacting with the system (ref: Arcadia). Like Primary Assets, Functions can define values for Confidentiality, Integrity, Availability and Traceability.

Data Storage Indicates that the function represents a data storage functionality. Yes/No
Remanent Data Indicates that the function manipulates data in such a way that data (or parts of it) remains even after attempts have been made to remove or erase it. Yes/No

Exchange Item

A Exchange Item describes a set of Data semantically coherent with regards to their usage in a given context: same communication principles, simultaneity of transportation, same non functional properties, indivisibility (an Exchange Item is monolithic). (ref. Arcadia) An Information Primary Asset references one or more Exchange Items. An Exchange Item can define values for Confidentiality, Integrity, Availability and Traceability.

Diagrams

The following diagram types are provided by the Capella Cybersecurity Viewpoint:

To create a Diagram, select the corresponding hyperlink from the Activity Explorer:

Threat Diagram

Threat diagrams are used to model System Threats, threatened Assets and Involved Actors:

Alternatively, select New Diagram/Table...->Threat Diagram on a component's context menu in the Capella Project Explorer.

The following tools are available:

Threat Create a new Threat.
Functional Primary Asset Create a new Functional Primary Asset.
Information Primary Asset Create a new Information Primary Asset.
Actor Create a new Actor.
Involves Create a new Threat Involvement between the selected Threat and Actor.
Applicable to Create a new Threat Application between the selected Threat and Primary Asset.
Actors Insert/Remove Actors. Create or delete graphical objects corresponding to already existing Actors. Removing an Actor graphical object from the diagram does not delete the Actor from the model. This tool does not modify the semantic model.
Threats Insert/Remove Threats. Create or delete graphical objects corresponding to already existing Threats. Removing a Threat graphical object from the diagram does not delete the Threat from the model. This tool does not modify the semantic model.
Functional Primary Assets Insert/Remove Functional Assets. Create or delete graphical objects corresponding to already existing Functional Assets. Removing a Functional Asset graphical object from the diagram does not delete the Functional Asset from the model. This tool does not modify the semantic model.
Information Primary Assets Insert/Remove Information Assets. Create or delete graphical objects corresponding to already existing Information Assets. Removing a Information Asset graphical object from the diagram does not delete the Information Asset from the model. This tool does not modify the semantic model.

Threat Level Decoration Layer

Threat diagrams have an optional layer named "Threat Level Decorations". When this layer is enabled, each Threat's level value is displayed in parenthesis on the up right corner of the Threat element:

Architecture Diagram

Architecture Diagrams are extended Capella Physical Architecture Diagrams. Thus, most of the tools available in Cybersecurity PAB diagrams are documented here.

One additional tool is provided by the Viewpoint:

Primary Assets Insert/Remove Primary Assets. Create or delete graphical objects corresponding to already existing Primary Assets. Removing a Primary Asset graphical object from the diagram does not delete the Primary Asset from the model. This tool does not modify the semantic model.. When a Primary Asset is added to a diagram, its color is chosen randomly from a set of predefined colors. Node elements related to the asset will then receive an emphasized border that matches the color of the asset element. Related edges will change the color to the color of the asset element.

Cybersecurity PAB Layer Extensions

Several Layers are provided for Cybersecurity PAB, PDFB, CDB and ES diagrams. A layer allows to change the presentation of a diagram in order to focus on specific aspects of the modeled system. Layers are activated in the diagram toolbar:

Trust Boundaries Layer

The Trust Boundaries Layer will change the diagrams appearence: Trusted components and actors will change their background color to white, untrusted components and actors will change their color to red. Communication edges between Trusted and Untrusted elements, so called Trust Boundaries, will be decorated with a small flame icon:

CIAT Layers

Additional layers are provided to focus on Confidentiality, Integrity, Availability and Traceability needs for model elements. When one of these layers is active, elements with a higher respective security needs value are emphasized over elements with a lower security needs value:

Cybersecurity Decorations Layer

The Cybersecurity Decorations Layer adds the following decorations to existing diagram elements.

Data Storage Indicates that the function represents a data storage functionality.
Trusted Actor Ability to be relied on as honest or truthful.
Untrusted Actor Disability to be relied on as honest or truthful.
Remanent Data Indicates that the function manipulates data in such a way that data (or parts of it) remains even after attempts have been made to remove or erase it.
ThreatSource Someone or something that could affect the product (ref: 87210649-DDQ-GRP-EN - Cyber Security For Architects Guide).

Scenario Diagram

See Capella Exchange Scenario Documentation.

Information Asset Diagram

See Capella Class Diagram Documentation.

Model Validation

Cybersecurity model elements and their attributes and relationships are subject to certain constraints. These constraints can be verified by selecting Validate->Validate Model from any model element's context menu.