A penetration test is a type of security assessment that simulates a real-world attack on a system or network, with the permission and authorization of the owner, to identify and exploit the vulnerabilities and weaknesses that may compromise the security of the system or network. A penetration test can help to evaluate the effectiveness and resilience of the security controls and measures that are implemented on the system or network, as well as to provide recommendations and solutions to improve the security posture of the system or network. One of the primary challenges when running a penetration test is determining the depth of coverage. The depth of coverage is the extent and level of detail that the penetration test will cover in terms of the scope, objectives, and methodology of the test. The depth of coverage can vary depending on the type, purpose, and budget of the penetration test, as well as the expectations and requirements of the organization and the stakeholders. The depth of coverage can affect the quality and accuracy of the penetration test results, as well as the time and resources that are needed to conduct the penetration test. Therefore, determining the depth of coverage is a critical and challenging task when running a penetration test, as it requires a careful balance and trade-off between the security and business needs of the organization and the stakeholders. Determining the cost, establishing a business case, or remediating found vulnerabilities are not the primary challenges when running a penetration test, as they are more related to the management, justification, or improvement aspects of the penetration test. References: CISSP All-in-One Exam Guide, Eighth Edition, Chapter 18: Security Assessment and Testing, page 1003; CISSP Official (ISC)2 Practice Tests, Third Edition, Domain 6: Security Assessment and Testing, Question 6.10, page 246.