| Information flow control regulates where information is allowed to travel within an information system and between information systems (as opposed to who is allowed to access the information) and without explicit regard to subsequent accesses to that information.
From an application perspective, flow control is established once application data flow modeling has been completed. Data flow modeling can be described as: the process of identifying, modeling and documenting how data moves around an information system. Data flow modeling examines processes (activities that transform data from one form to another), data stores (the holding areas for data), external entities (what sends data into a system or receives data from a system), and data flows (routes by which data can flow).
Once the application data flows have been identified, corresponding flow controls can be applied at the appropriate points.
A few examples of flow control restrictions include: keeping export controlled information from being transmitted in the clear to the Internet and blocking information marked as classified but is being transported to an unapproved destination. Information flow control policies and enforcement mechanisms are commonly employed by organizations to control the flow of information between designated sources and destinations (e.g., networks, individuals, devices) within information systems and between interconnected systems. Flow control is based on the characteristics of the information and/or the information path.
Application specific examples of flow control enforcement can be found in information protection software (e.g., guards, proxies, gateways and cross domain solutions) employing rule sets or establish configuration settings restricting information system services or provide message filtering capability based on content (e.g., using key word searches or document characteristics).
A crucial part of any flow control solution is the ability to create policy filters. Policy filters serve to enact and enforce the organizational policy as it pertains to controlling data flow.
Organization-defined security policy filters include, file type checking filters, structured data filters, unstructured data filters, metadata content filters, and hidden content filters.
- Structured data permits the interpretation of its content by virtue of atomic elements that are understandable by an application and indivisible.
- Unstructured data refers to masses of (usually) digital information does not have a data structure or does have a data structure that is not easily readable by a machine. Unstructured data consists of two basic categories: (i) bitmap objects that are inherently non language-based (i.e., image, video, or audio files); and (ii) textual objects based on a written or printed language (i.e., commercial off-the-shelf word processing documents, spreadsheets, or emails).
Applications providing information flow control must provide the capability for privileged administrators to configure security policy filters to support different security policies.
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