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

was the actual entity controlling that user account when the undesired action took place.

      To have viable accountability, you must be able to support your security in a court of law. If you are unable to legally support your security efforts, then you will be unlikely to be able to hold a human accountable for actions linked to a user account. With only a password as authentication, there is significant room for doubt. Passwords are the least secure form of authentication, with dozens of different methods available to compromise them. However, with the use of multifactor authentication, such as a password, smartcard, and fingerprint scan in combination, there is very little possibility that any other human could have compromised the authentication process in order to impersonate the human responsible for the user account.

       Legally Defensible Security

      The point of security is to keep bad things from happening while supporting the occurrence of good things. When bad things do happen, organizations often desire assistance from law enforcement and the legal system for compensation. To obtain legal restitution, you must demonstrate that a crime was committed, that the suspect committed that crime, and that you took reasonable efforts to prevent the crime. This means your organization’s security needs to be legally defensible. If you are unable to convince a court that your log files are accurate and that no other person other than the subject could have committed the crime, you will not obtain restitution. Ultimately, this requires a complete security solution that has strong multifactor authentication techniques, solid authorization mechanisms, and impeccable auditing systems. Additionally, you must show that the organization complied with all applicable laws and regulations, that proper warnings and notifications were posted, that both logical and physical security were not otherwise compromised, and that there are no other possible reasonable interpretations of the electronic evidence. This is a fairly challenging standard to meet. If you are not going to make the effort to design and implement legally defensible security, what is the point in attempting subpar security?

      Nonrepudiation

      Nonrepudiation ensures that the subject of an activity or event cannot deny that the event occurred. Nonrepudiation prevents a subject from claiming not to have sent a message, not to have performed an action, or not to have been the cause of an event. It is made possible through identification, authentication, authorization, accountability, and auditing. Nonrepudiation can be established using digital certificates, session identifiers, transaction logs, and numerous other transactional and access control mechanisms. If nonrepudiation is not built into a system and properly enforced, you will not be able to verify that a specific entity performed a certain action. Nonrepudiation is an essential part of accountability. A suspect cannot be held accountable if they can repudiate the claim against them.

Protection Mechanisms

      Another aspect of understanding and apply concepts of confidentiality, integrity, and availability is the concept of protection mechanisms. Protection mechanisms are common characteristics of security controls. Not all security controls must have them, but many controls offer their protection for confidentiality, integrity, and availability through the use of these mechanisms. These mechanisms include using multiple layers or levels of access, employing abstraction, hiding data, and using encryption.

Layering

      Layering, also known as defense in depth, is simply the use of multiple controls in a series. No one control can protect against all possible threats. Using a multilayered solution allows for numerous, different controls to guard against whatever threats come to pass. When security solutions are designed in layers, most threats are eliminated, mitigated, or thwarted.

      Using layers in a series rather than in parallel is important. Performing security restrictions in a series means to perform one after the other in a linear fashion. Only through a series configuration will each attack be scanned, evaluated, or mitigated by every security control. In a series configuration, failure of a single security control does not render the entire solution ineffective. If security controls were implemented in parallel, a threat could pass through a single checkpoint that did not address its particular malicious activity.

      Serial configurations are very narrow but very deep, whereas parallel configurations are very wide but very shallow. Parallel systems are useful in distributed computing applications, but parallelism is not often a useful concept in the realm of security.

      Think of physical entrances to buildings. A parallel configuration is used for shopping malls. There are many doors in many locations around the entire perimeter of the mall. A series configuration would most likely be used in a bank or an airport. A single entrance is provided, and that entrance is actually several gateways or checkpoints that must be passed in sequential order to gain entry into active areas of the building.

      Layering also includes the concept that networks comprise numerous separate entities, each with its own unique security controls and vulnerabilities. In an effective security solution, there is a synergy between all networked systems that creates a single security front. Using separate security systems creates a layered security solution.

Abstraction

      Abstraction is used for efficiency. Similar elements are put into groups, classes, or roles that are assigned security controls, restrictions, or permissions as a collective. Thus, the concept of abstraction is used when classifying objects or assigning roles to subjects. The concept of abstraction also includes the definition of object and subject types or of objects themselves (that is, a data structure used to define a template for a class of entities). Abstraction is used to define what types of data an object can contain, what types of functions can be performed on or by that object, and what capabilities that object has. Abstraction simplifies security by enabling you to assign security controls to a group of objects collected by type or function.

Data Hiding

      Data hiding is exactly what it sounds like: preventing data from being discovered or accessed by a subject by positioning the data in a logical storage compartment that is not accessible or seen by the subject. Forms of data hiding include keeping a database from being accessed by unauthorized visitors and restricting a subject at a lower classification level from accessing data at a higher classification level. Preventing an application from accessing hardware directly is also a form of data hiding. Data hiding is often a key element in security controls as well as in programming.

Encryption

      Encryption is the art and science of hiding the meaning or intent of a communication from unintended recipients. Encryption can take many forms and be applied to every type of electronic communication, including text, audio, and video files as well as applications themselves. Encryption is an important element in security controls, especially in regard to the transmission of data between systems. There are various strengths of encryption, each of which is designed and/or appropriate for a specific use or purpose. Encryption is discussed at length in Chapter 6, “Cryptography and Symmetric Key Algorithms,” and Chapter 7, “PKI and Cryptographic Applications.”

      Apply Security Governance Principles

      Security governance is the collection of practices related to supporting, defining, and directing the security efforts of an organization. Security governance is closely related to and often intertwined with corporate and IT governance. The goals of these three governance agendas are often the same or interrelated. For example, a common goal of organizational governance is to ensure that the organization will continue to exist and will grow or expand over time. Thus, the common goal of governance is to maintain business processes while striving toward growth and resiliency.

      Some aspects of governance are imposed on organizations due to legislative and regulatory compliance needs, whereas others are imposed by industry guidelines or license requirements. All forms of governance, including security governance, must be assessed and verified from time to time. Various requirements for auditing and validation may be present due to government regulations or industry best practices. Governance compliance issues often vary from industry to industry and from country to country. As many organizations expand and adapt to deal with a global market, governance issues become more complex. This is especially problematic when laws in different countries differ or in fact conflict. The organization as a whole should be given the direction, guidance, and tools to provide sufficient oversight and management to address threats and risks with a focus on eliminating