During the containment phase, the immediate response to an incident involves limiting its scope and magnitude, which includes preserving evidence. This is crucial for a subsequent forensic analysis and for learning lessons from the incident to prevent future occurrences.
Reference = The containment phase is part of the incident response process as outlined in ISACA's resources, which include steps such as detection and analysis, containment, eradication, recovery, and post-incident activities12.

An objective of public key infrastructure (PKI) is to independently authenticate the validity of the sender's public key. PKI is a system that uses cryptographic keys to secure communications and transactions. PKI involves a trusted third party called a certificate authority (CA) that issues digital certificates that link a public key with an identity. The recipient can use the CA's public key to verify the sender's certificate and public key.

A passive activity that could be used by an attacker during reconnaissance to gather information about an organization is using open source discovery. This is because open source discovery is a technique that involves collecting and analyzing publicly available information about an organization, such as its website, social media, press releases, annual reports, etc. Open source discovery does not require any direct interaction or communication with the target organization or its systems or network, and therefore does not generate any traffic or alerts that could be detected by the organization's security controls. The other options are not passive activities that could be used by an attacker during reconnaissance to gather information about an organization, but rather active activities that involve direct or indirect interaction or communication with the target organization or its systems or network, such as scanning the network perimeter (B), social engineering C, or crafting counterfeit websites (D).

The BEST feature that facilitates the development of metrics for reporting to senior management on vulnerability management efforts is tracking vulnerabilities and the remediation efforts to mitigate them. This is because tracking vulnerabilities and remediation efforts helps to measure and monitor the performance and effectiveness of vulnerability management efforts, by providing quantifiable and objective data on the number, severity, impact, status, and resolution time of vulnerabilities. Tracking vulnerabilities and remediation efforts also helps to identify and communicate any gaps or issues in vulnerability management efforts to senior management and other stakeholders. The other options are not features that facilitate the development of metrics for reporting to senior management on vulnerability management efforts, but rather different aspects or factors that affect vulnerability management efforts, such as reviewing business impact analysis (BIA) results (A), benchmarking with industry peers (B), or monitoring the frequency of vulnerability assessments (D).

Explanation
An example of an attack attribute of an advanced persistent threat (APT) that is designed to remove data from systems and networks is an exfiltration attack vector. An exfiltration attack vector is a method or channel that an APT uses to transfer data from a compromised system or network to an external location. Examples of exfiltration attack vectors include email, FTP, DNS, HTTP, or covert channels.