CISSP (ISC)2 Certified Information Systems Security Professional Official Study Guide - Gibson Darril

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or end results of an attack. Attempting to identify each and every specific attack method and technique is an impossible task – new attacks are being developed constantly. Although the goals or purposes of attacks can be loosely categorized and grouped, they remain relatively constant over time.

       Be Alert for Individual Threats

      Competition is often a key part of business growth, but overly adversarial competition can increase the threat level from individuals. In addition to criminal hackers and disgruntled employees, adversaries, contractors, employees, and even trusted partners can be a threat to an organization if relationships go sour.

      ■ Never assume that a consultant or contractor has the same loyalty to your organization as a long-term employee. Contractors and consultants are effectively mercenaries who will work for the highest bidder. Don’t take employee loyalty for granted either. Employees who are frustrated with their working environment or feel they’ve been treated unfairly may attempt to retaliate. An employee experiencing financial hardship may consider unethical and illegal activities that pose a threat to your business for their own gain.

      ■ A trusted partner is only a trusted partner as long as it is in your mutual self-interest to be friendly and cooperative toward each other. Eventually a partnership might sour or become adversarial; then, your former partner might take actions that pose a threat to your business.

      Potential threats to your business are broad and varied. A company faces threats from nature, technology, and people. Most businesses focus on natural disasters and IT attacks in preparing for threats, but it’s also important to consider threat potential from individuals. Always consider the best and worst possible outcomes of your organization’s activities, decisions, interactions. Identifying threats is the first step toward designing defenses to help reduce or eliminate downtime, compromise, and loss.

Determining and Diagramming Potential Attacks

Once an understanding has been gained in regard to the threats facing your development project or deployed infrastructure, the next step in threat modeling is to determine the potential attack concepts that could be realized. This is often accomplished through the creation of a diagram of the elements involved in a transaction along with indications of data flow and privilege boundaries (Figure 1.7).

Figure 1.7 An example of diagramming to reveal threat concerns

      Such data flow diagrams are useful in gaining a better understanding of the relationships of resources and movement of data through a visual representation. This process of diagramming is also known as crafting an architecture diagram. The creation of the diagram helps to detail the functions and purpose of each element of a business task, development process, or work activity. It is important to include users, processors, applications, datastores, and all other essential elements needed to perform the specific task or operation. This is a high-level overview and not a detailed evaluation of the coding logic. However, for more complex systems, multiple diagrams may need to be created at various focus points and at varying levels of detail magnification.

      Once a diagram has been crafted, identify all of the technologies involved. This would include operating systems, applications (network service and client based), and protocols. Be specific as to the version numbers and update/patch level in use.

      Next, identify attacks that could be targeted at each element of the diagram. Keep in mind that all forms of attacks should be considered, including logical/technical, physical, and social. For example, be sure to include spoofing, tampering, and social engineering. This process will quickly lead you into the next phase of threat modeling: reduction analysis.

Performing Reduction Analysis

      The next step in threat modeling is to perform reduction analysis. Reduction analysis is also known as decomposing the application, system, or environment. The purpose of this task is to gain a greater understanding of the logic of the product as well as its interactions with external elements. Whether an application, a system, or an entire environment, it needs to be divided into smaller containers or compartments. Those might be subroutines, modules, or objects if you’re focusing on software, computers, or operating systems; they might be protocols if you’re focusing on systems or networks; or they might be departments, tasks, and networks if you’re focusing on an entire business infrastructure. Each identified subelement should be evaluated in order to understand inputs, processing, security, data management, storage, and outputs.

      In the decomposition process, you must identify five key concepts:

      Trust Boundaries Any location where the level of trust or security changes

      Data Flow Paths The movement of data between locations

      Input Points Locations where external input is received

      Privileged Operations Any activity that requires greater privileges than of a standard user account or process, typically required to make system changes or alter security

      Details about Security Stance and Approach The declaration of the security policy, security foundations, and security assumptions

      Breaking down a system into its constituent parts makes it much easier to identity the essential components of each element as well as take notice of vulnerabilities and points of attack. The more you understand exactly how a program, system, or environment operates, the easier it is to identity threats to it.

Prioritization and Response

      As threats are identified through the threat modeling procedure, additional activities are prescribed to round out the process. Next is to fully document the threats. In this documentation, you should define the means, target, and consequences of a threat. Consider including the techniques required to implement an exploitation as well as list potential countermeasures and safeguards.

      After documentation, rank or rate the threats. This can be accomplished using a wide range of techniques, such as Probability × Damage Potential ranking, high/medium/low rating, or the DREAD system.

      The ranking technique of Probability × Damage Potential produces a risk severity number on a scale of 1 to 100, with 100 the most severe risk possible. Each of the two initial values can be assigned numbers between 1 and 10, with 1 being lowest and 10 being highest. These rankings can be somewhat arbitrary and subjective, but since the same person or team will be assigning the numbers for their own organization, it should still result in assessment values that are accurate on a relative basis.

      The high/medium/low rating process is even simpler. Each threat is assigned one of these three priority labels. Those given the high-priority label need to be addressed immediately. Those given the medium-priority label should be addressed eventually, but they don’t require immediate action. Those given the low-priority level might be addressed, but they could be deemed optional if they require too much effort or expense in comparison to the project as a whole.

      The DREAD rating system is designed to provide a flexible rating solution that is based on the answers to five main questions about each threat:

      ■ Damage potential – How severe is the damage likely to be if the threat is realized?

      ■ Reproducibility – How complicated is it for attackers to reproduce the exploit?

      ■ Exploitability – How hard is it to perform the attack?

      ■ Affected users – How many users are likely to be affected by the attack (as a percentage)?

      ■ Discoverability – How hard is it for an attacker to discover the weakness?

      By asking these and potentially additional customized questions, along with assigning H/M/L or 3/2/1 values to the answers, you can establish a detailed threat prioritization.

      Once threat priorities are set, responses to those threats need to be determined. Technologies and processes to remediate threats should be considered and weighted according to their cost and effectiveness. Response options should include making adjustments to software architecture, altering operations and processes, as well as

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