Which of the following access control models are used in the commercial sector? Each correct answer represents a complete solution. Choose two.
Answer(s): A,C
The Biba and Clark-Wilson access control models are used in the commercial sector. The Biba model is a formal state transition system of computer security policy that describes a set of access control rules designed to ensure data integrity. Data and subjects are grouped into ordered levels of integrity. The model is designed so that subjects may not corrupt data in a level ranked higher than the subject, or be corrupted by data from a lower level than the subject. The Clark-Wilson security model provides a foundation for specifying and analyzing an integrity policy for a computing system. Answer D is incorrect. The Bell-LaPadula access control model is mainly used in military systems. Answer B is incorrect. There is no such access control model as Clark-Biba.
Which of the following testing methods verifies the interfaces between components against a software design?
Answer(s): B
Integration testing is a software testing that seeks to verify the interfaces between components against a software design. Software components may be integrated in an iterative way or all together ("big bang"). Normally the former is considered a better practice since it allows interface issues to be localized more quickly and fixed. Integration testing works to expose defects in the interfaces and interaction between the integrated components (modules). Progressively larger groups of tested software components corresponding to elements of the architectural design are integrated and tested until the software works as a system. Answer A is incorrect. Regression testing focuses on finding defects after a major code change has occurred. Specifically, it seeks to uncover software regressions, or old bugs that have come back. Such regressions occur whenever software functionality that was previously working correctly stops working as intended. Typically, regressions occur as an unintended consequence of program changes, when the newly developed part of the software collides with the previously existing code. Answer D is incorrect. Unit testing refers to tests that verify the functionality of a specific section of code, usually at the function level. In an object-oriented environment, this is usually at the class level, and the minimal unit tests include the constructors and destructors. These types of tests are usually written by developers as they work on code (white-box style), to ensure that the specific function is working as expected. One function might have multiple tests, to catch corner cases or other branches in the code. Unit testing alone cannot verify the functionality of a piece of software, but rather is used to assure that the building blocks the software uses work independently of each other. Answer C is incorrect. The black-box testing uses external descriptions of the software, including specifications, requirements, and design to derive test cases. These tests can be functional or non-functional, though usually functional. The test designer selects valid and invalid inputs and determines the correct output. There is no knowledge of the test object's internal structure. This method of test design is applicable to all levels of software testing: unit, integration, functional testing, system and acceptance. The higher the level, and hence the bigger and more complex the box, the more one is forced to use black box testing to simplify. While this method can uncover unimplemented parts of the specification, one cannot be sure that all existent paths are tested.
Which of the following statements best describes the difference between the role of a data owner and the role of a data custodian?
Answer(s): D
The data owner is responsible for ensuring that the appropriate security controls are in place, for assigning the initial classification to the data to be protected, for approving access requests from other parts of the organization, and for periodically reviewing the data classifications and access rights. Data owners are primarily responsible for determining the data's sensitivity or classification levels, whereas the data custodian has the responsibility for backup, retention, and recovery of data. The data owner delegates these responsibilities to the custodian. Answers B, A, and C are incorrect. These are not the valid answers.
Della works as a security engineer for BlueWell Inc. She wants to establish configuration management and control procedures that will document proposed or actual changes to the information system. Which of the following phases of NIST SP 800-37 C&A methodology will define the above task?
Answer(s): C
The various phases of NIST SP 800-37 C&A are as follows:Phase 1: Initiation- This phase includes preparation, notification and resource identification. It performs the security plan analysis, update, and acceptance. Phase 2: Security Certification- The Security certification phase evaluates the controls and documentation. Phase 3: Security Accreditation- The security accreditation phase examines the residual risk for acceptability, and prepares the final security accreditation package. Phase 4: Continuous Monitoring-This phase monitors the configuration management and control, ongoing security control verification, and status reporting and documentation.
Which of the following secure coding principles and practices defines the appearance of code listing so that a code reviewer and maintainer who have not written that code can easily understand it?
Use a consistent coding style is one of the principles and practices that contribute to defensive coding. This principle defines the appearance of code listing so that a code reviewer and maintainer who have not written that code can easily understand it. For this purpose, all programmers of a team must follow the same guidelines. Answer D is incorrect. Keep code simple and small defines that it is easy to verify the software security when a programmer uses small and simple code base. Answer A is incorrect. Make code forward and backward traceable defines that traceability is necessary in order to validate requirements, prevent defects, and find and solve inconsistencies among all objects generated in the SDLC phases. Answer B is incorrect. Review code during and after coding defines that code must be examined in order to identify coding errors in modules.
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