Black box testing is generally used when the tester has limited knowledge of the system under test or when access to source code is not available. Within the security test arena, black box testing is normally associated with activities that occur during the pre-deployment test phase (system test) or on a periodic basis after the system has been deployed.
Black box security tests are conducted to identify and resolve potential security vulnerabilities before deployment or to periodically identify and resolve security issues within deployed systems. They can also be used as a “badness-ometer” [McGraw 04] to give an organization some idea of how bad the security of their system is. From a business perspective, organizations conduct black box security tests to conform to regulatory requirements, protect confidentially and proprietary information and protect the organization’s brand and reputation.
Fortunately, a significant number of black box test tools focus on application security related issues. These tools concentrate on security-related issues including but not limited to:
- Input checking and validation
- SQL insertion attacks
- Injection Flaws
- Session management issues
- cross-site scripting attacks
- Buffer overflow vulnerabilities
- Directory traversal attacks
Benefits and Limitations of Black Box Testing
As previously discussed, black box tests are generally conducted when the tester has limited knowledge of the system under test or when access to source code is not available. On its own, black box testing is not a suitable alternative for security activities throughout the software development life cycle. These activities include the development of security-based requirements, risk assessments, security-based architectures, white box security tests, and code reviews. However, when used to complement these activities or to test third-party applications or security-specific subsystems, black box test activities can provide a development staff crucial and significant insight regarding the system’s design and implementation.
Black box tests can help development and security personnel to:
- Identify implementation errors that were not discovered during code reviews, unit tests, or security white box tests
- Discover potential security issues resulting from boundary conditions that were difficult to identify and understand during the design and implementation phases
- Uncover security issues resulting from incorrect product builds (e.g., old or missing modules/files)
- Detect security issues that arise as a result of interaction with the underlying environment (e.g., improper configuration files, unhardened OS, and applications)