Encrypted file transfer (external)

This example is of applying trust models to develop a security architecture that can be applied to an externally accessible file transfer solution.

The numbers in the diagram will be explained as we progress through the scenario.

We will start by first referencing our data-centric architecture diagram from Chapter 2, Security Architectures.

With the designed solution we must consider each layer of the above diagram and determine what security mechanisms must be employed to secure the data interaction. In order to determine this, it must first be understood what data will be interacted with, what process the solution is supporting, applications that may be used, and users who will be using the solution.

Let's start with identifying each component of the trust model by building blocks for this file transfer solution.

Data types	Process(s)	Application(s)	Users	Roles	Policies and standards
PII	Prescription order fulfillment	Prescription order fulfillment system	External Internal	User Administrator Data owner	Data classification Data handling Encryption standard Third party authentication standard

Now that we have defined all the building blocks of our trust model, risk can be assessed and security mechanisms can be chosen.

If there are regulatory requirements for the data in the solution, these will have a significant influence on what security must be implemented. If policies and standards have been developed that need to be applied more direction, then they can be derived from the content of these documents.

Tip

It may become apparent that there are missing policies and standards to properly enforce the requirement for security controls. If this is the case and not too significant a risk, then note the present shortcomings, obtain approval from those who can assume risk, and begin the process to correct the identified gaps. It is common for new solutions, projects, and market shifts to drive new security policies and standards.

We now have what is needed to develop our trust models that will drive the security architecture applied to the solution design. Because the trust in this case is based on the user and the data being transferred, we'll focus on these trust models.

External user

User type	External
Trust level	1 – not trusted
Allowed access	Tier 1 DMZ only, least privilege
Required security mechanisms	FW, IPS, data encryption, user authentication, and role enforcement

Internal user

User type	Internal
Trust level	3 – trusted
Allowed access	Internal network systems, least privilege
Required security mechanisms	FW, IPS, data encryption, user authentication, and role enforcement

Data owner

User type	Internal
Trust level	3 –trusted
Allowed access	Internal network systems, least privilege
Required security mechanisms	FW, IPS, data encryption, user authentication, and role enforcement

Automation

User type	Automation
Trust level	2 – median trusted
Allowed access	Least privilege
Required security mechanisms	FW, IPS, file integrity monitoring, and data loss prevention

With the building blocks defined and trust models developed, a data-centric security architecture can be applied to the file transfer design to maximize security and minimize risk. We will now see how the applied security architecture is implemented in the reference architecture for encrypted file transfer accessible to external parties.

Label	Description	Purpose
1	Internal user authentication	Role enforcement and least privilege implementation
2	Encryption key management	Necessary to provide encryption meeting policy and standard requirements
3	Secure network communication	Data protection, data handling per data classification policy, and encryption standards enforcement
4	Automation (file delivery)	Process used to enforce least privilege and provide necessary external and internal separation
5	External user authentication	Role enforcement and least privilege implementation
6	Secure file transfer system	Data protection, data handling per data classification policy, and encryption standards enforcement
7	Encrypted file transmission	Data protection, data handling per data classification policy, and encryption standards enforcement

I have inserted the diagram again for ease of understanding the preceding table.

This example is an exercise that should eventually become second nature when developing new solutions or data interactions. Much of what the trust models provide should become standards and a requirements checklist for projects. The key is to provide an agile approach to securing solutions and data interaction that are not confined by the network design. As we have covered in Chapter 2, Security Architectures, there is little control over the network design as BYOD and cloud initiatives infiltrate the once trusted internal sanctuary of the enterprise network.