The BEST basis for allocating proportional protection activities when comprehensive classification is not feasible is a business dependency assessment. This is because a business dependency assessment helps to identify the criticality and sensitivity of business processes and their supporting assets, based on their contribution to the organization’s objectives and value proposition. This allows for prioritizing protection activities according to the level of risk and impact. The other options are not as effective as a business dependency assessment, because they either use a single classification level allocation (A), which does not account for different levels of risk and impact; require a significant amount of time and resources to perform a business process re-engineering (B); or rely on external parties to cover potential losses without reducing the likelihood or impact of incidents (D) 

Availability can be protected through the use of redundancy, backups, and business continuity management. This is because these measures help to ensure that systems, data, and services are accessible and functional at all times, even in the event of a disruption or disaster. The other options are not directly related to protecting availability, but rather focus on enhancing confidentiality (A), integrity C, or awareness (D).

The second line of defense in cybersecurity includes risk management monitoring, and measurement of controls. This is because the second line of defense is responsible for ensuring that the first line of defense (the operational managers and staff who own and manage risks) is effectively designed and operating as intended. The second line of defense also provides guidance, oversight, and challenge to the first line of defense. The other options are not part of the second line of defense, but rather belong to the first line of defense (A), the third line of defense C, or an external service provider (D). 

The “recover” function of the NIST cybersecurity framework is concerned with planning for resilience and timely repair of compromised capacities and service. This is because the recover function helps organizations to restore normal operations as quickly as possible after a cybersecurity incident, while also learning from the incident and improving their security posture. The other options are not part of the recover function, but rather belong to the identify (B), respond C, or protect (D) functions. 

The backup procedure that would only copy files that have changed since the last backup was made is an incremental backup. This is because an incremental backup is a type of backup that only copies the files that have been created or modified since the previous backup, whether it was a full or an incremental backup. An incremental backup helps to reduce the backup time and storage space, as well as the recovery time, as only the changed files need to be restored. The other options are not backup procedures that would only copy files that have changed since the last backup was made, but rather different types of backup procedures that copy files based on different criteria, such as daily backup (B), differential backup C, or full backup (D).

Key risk indicators (KRIs) are metrics that can provide an early signal of increasing risk exposures for an organization. KRIs are designed to measure and predict potential losses, and they help in identifying trends that could lead to future risks. They are different from Key Performance Indicators (KPIs), which measure the performance related to the achievement of strategic goals. KRIs, on the other hand, are specifically focused on risk and are used to monitor changes in the level of risk exposure.
References:  The information is supported by ISACA’s resources, which state that KRIs with thresholds and corresponding trigger actions can enable companies to gain visibility into risks before they occur.  These metrics best position enterprises to deal with substantial cyber risks associated with digital transformation and implementing emerging technologies 1 .

Tracing the access and origin of an intrusion is crucial for performing a root cause analysis. This process involves identifying the underlying factors that led to the security breach. By understanding how the intrusion happened, organizations can better address the specific vulnerabilities that were exploited and implement more effective security measures to prevent similar incidents in the future.

References : ISACA’s resources on cybersecurity audit emphasize the importance of root cause analysis in the event of an intrusion.  It is a key step in the cybersecurity audit process to understand the weaknesses that led to the incident and to improve the overall security posture of the organization 1 .

System hardening is a process that involves implementing security measures to reduce the system’s vulnerability. The main purpose of this process is to limit the number of attack vectors that can be exploited by threats. By removing unnecessary programs, closing unused ports, and applying security patches, the system’s attack surface is reduced, making it more difficult for attackers to find vulnerabilities to exploit.
References:  The concept of system hardening is covered in ISACA’s resources as a means to protect information assets by addressing threats to information processed, stored, and transported by internetworked information systems 1 .  It is a collection of tools and techniques aimed at reducing vulnerability in various areas of an IT system 2 .