CompTIA CS0-003 - CompTIA CyberSecurity Analyst CySA+ Certification Exam

This answer matches the description of the zero-day threat. The attack vector is network (AV:N), the attack complexity is low (AC:L), no privileges are required (PR:N), no user interaction is required (UI:N), the scope is unchanged (S:U), the confidentiality and integrity impacts are high (C:H/I:H), and the availability impact is low (A:L). Official References: https://nvd.nist.gov/vuln-metrics/cvss

Using CVSS v4.0, the highest-priority remediation is typically the vulnerability that is most remotely exploitable and requires the least attacker effort (low complexity, no special conditions, low/no privileges, and no user interaction).

System D is the strongest “fix first” candidate because it combines:

AV:N (Network) → remotely exploitable over the network; severity increases the more remote the attacker can be.

AC:L (Low) → easier to exploit than High complexity.

AT:N (None) → “does not depend on deployment/execution conditions”; attacker can expect the exploit to work under most instances.

PR:L (Low) → only basic user privileges required (still relatively accessible).

UI:N (None) → most important differentiator vs System A. CVSS v4.0 explicitly states: “The resulting score is greatest when no user interaction is required.”

E:P (Proof-of-Concept) → publicly available PoC code exists (more exploitable than “Unreported”), increasing urgency compared to U.

Why not System A (the closest competitor)?

System A is also AV:N/AC:L/AT:N/PR:L, but it has UI:A (Active), meaning exploitation requires a targeted user to perform specific actions. CVSS v4.0 defines Active (A) as requiring “specific, conscious interactions… or actively subvert protection mechanisms.”

System D’s UI:N makes it exploitable purely at the attacker’s will, which CVSS treats as more severe.

Why the others are lower priority

System B (AV:A, AC:H, AT:P): adjacent-only, high complexity, and attack requirements present → significantly harder/less broadly exploitable.

System C (AV:P) and System E (AV:P): require physical access, which reduces the pool of potential attackers and generally lowers priority versus network-exploitable issues.

References (Official CVSS v4.0 specification used):

FIRST, CVSS v4.0 Specification Document:

User Interaction values (None/Passive/Active) and “score is greatest when no user interaction is required”

Attack Requirements (AT) definitions (None vs Present)

Exploit Maturity (E) values (X/A/P/U) and meanings

Attack Vector remoteness increases severity

To improve the detection of known attacks and behavioralIndicators of Compromise (IoCs), the best approach is tointegrate with an open-source threat intelligence feed. Threat intelligence feeds provide up-to-date information on known malicious IPs, domains, file hashes, and behavioral patterns that attackers use​.

Option A (randomly generating and storing hash values)is impractical, as there are an infinite number of possible files.

Option B (alerting on any system change)would lead to excessive noise and false positives, making the system difficult to manage.

Option D (manually adding signatures)is useful but is not scalable or as timely as an external intelligence feed​.

Thus, the correct answer isC, as integrating an open-source threat intelligence feed enhances the SIEM’s ability to detect and respond to real-world threats​.

The incident response policy or plan is a document that defines the roles and responsibilities, procedures and processes, communication and escalation protocols, and reporting and documentation requirements for handling security incidents. The lead should review what is documented in the incident response policy or plan to determine who should be communicated with and when during a security incident, as well as what information should be shared and how. The incident response policy or plan should also be aligned with the organizational policies and legal obligations regarding incident notification and disclosure.

Root cause analysis (RCA) is a post-incident activity focused on identifying the underlying cause of an incident/problem so the organization can fix the real cause (not just symptoms) and prevent recurrence. That matches Option B, which describes tracing the origin and eliminating it permanently.

The Sybex CySA+ Study Guide defines RCA in exactly this way:

Exact extract (Sybex Study Guide):

“The process of root cause analysis (RCA) is used to identify why a problem, incident, or issue occurred. Root cause analysis is performed to allow organizations to understand what they need to focus on to prevent future problems…”

The Secbay Press guide also defines RCA as uncovering underlying causes to prevent recurrence:

Exact extract (Secbay Press):

“Root Cause Analysis (RCA)… is a systematic investigation process aimed at identifying the fundamental factors that led to a security incident. It goes beyond addressing symptoms and seeks to uncover the underlying causes to prevent recurrence.”

Why the other options are wrong

A (TTPs): That describes attacker behavior frameworks (e.g., MITRE ATT & CK), not RCA.

C (who/what/when/where/why): That’s an incident reporting structure, not the RCA process.

D (ongoing activities report): That resembles status reporting/incident updates, not root cause determination.

References (CompTIA CySA+ CS0-003 documents / study guides used):

Mike Chapple & David Seidl, CompTIA CySA+ Study Guide (CS0-003): RCA identifies why an incident occurred and helps prevent recurrence

Secbay Press, CompTIA CySA+ Exam Prep Guide (CS0-003): RCA goes beyond symptoms to uncover underlying causes and prevent recurrence

Secbay Press, CompTIA CySA+ Exam Prep Guide (CS0-003): “who/what/when/where/why” belongs to incident reporting context

The correct answer is B. CASB. A Cloud Access Security Broker is specifically designed to sit between users and cloud services, monitor cloud activity, enforce access policies, and provide visibility into unauthorized cloud storage use. This directly matches the question’s requirement: showing user access to prohibited cloud storage and whether a file was downloaded to a personal device.

Exact supporting extract: the All-in-One CySA+ guide explains that a CASB “sits between each user and each cloud service,” monitors activity, enforces policies, and alerts when something is wrong. It also lists visibility as a CASB pillar, including whether users are connecting to unauthorized resources such as cloud storage not controlled by the organization.

The Sybex CySA+ Study Guide also states that CASB tools enforce security policies when cloud resources and services are used, and can help with data security, service usage and access visibility, and risk management.

The official CompTIA CySA+ CS0-003 objectives include Cloud Access Security Broker (CASB) under identity and access management / security operations architecture concepts.

Why the other options are incorrect:

A. SASE is broader architecture that may include CASB, SWG, FWaaS, and SD-WAN, but the specific tool for cloud-service visibility and policy logging is CASB.

C. EDR focuses on endpoint detection and response, not cloud storage access monitoring across cloud services.

D. SDN is software-defined networking and does not provide user-level cloud storage access logs.

Eradication is a step in the incident response process that involves removing any traces or remnants of the incident from the affected systems or networks, such as malware, backdoors, compromised accounts, or malicious files. Eradication also involves restoring the systems or networks to their normal or secure state, as well as verifying that the incident is completely eliminated and cannot recur. In this case, the analyst is remediating items associated with a recent incident by isolating the vulnerabilityand actively removing it from the system. This describes the eradication step of the incident response process.