CompTIA CS0-003 Practice Test

Why Log Entry 1 Indicates a Command Injection Attempt:

Command injection vulnerabilities allow an attacker to inject and execute arbitrary commands on a host operating system via a vulnerable application. These commands are usually embedded in input fields, URLs, or headers.

If Log Entry 1 is showing something like: bash Copy Edit

GET /search?query=abc;cat%20/etc/passwd HTTP/1.1

GET /submit?name=John&&whoami

Then it is a strong indicator of command injection, because:

Semicolons (;), double ampersands (&&), or pipes (|) are used to chain system commands.

Commands like cat /etc/passwd, whoami, ls, ping, etc., are classic targets to verify code execution.

Use of URL encoding like %3B (which is ;) is another telltale sign of evasion attempts.

Why It’s Important:

This kind of activity in logs, especially right after a zero-day vulnerability is published, often means adversaries are:

Scanning for unpatched systems.

Trying proof-of-concept (PoC) payloads to validate the vulnerability.

Attempting to gain remote command execution or initial access.

Summary:

Log Entry 1 is correct because it likely shows classic command injection patterns—use of shell operators and system commands in user input. This aligns with what attackers would do after a zero-day command injection vulnerability is published.

Explanation:

This question refers to the output of a web application vulnerability assessment, and while we can’t see the image directly (src="https://selfexamtraining.com/uploadimages/CS0-003-Qu1.jpg"), we can infer from the options that the assessment identified issues related to Cross-Origin Resource Sharing (CORS). Let’s break down the most likely diagnosis and tuning recommendation:

Understanding the Core Issue: CORS Misconfiguration

The key clue is:

One of the options is: “Configure an Access-Control-Allow-Origin header to authorized domains”

This strongly implies the vulnerability scan found that the server is either

Not setting the Access-Control-Allow-Origin header at all, or

Setting it too permissively (e.g., *), which allows any origin to access the web resource via browser requests

This is a security risk, especially for applications dealing with:

Session cookies

User data

Private APIs

Amisconfigured CORS policy can allow malicious domains to make unauthorized cross-origin requests to your application and steal sensitive data, like session tokens.

Correct Remediation:

Configure an Access-Control-Allow-Origin header to only allow requests from trusted, authorized domains.

This limits cross-origin requests to only domains you control or trust (e.g., your frontend application hosted on another subdomain).

References:
OWASP CORS Misconfiguration Guide

MDN - Access-Control-Allow-Origin

NIST SP 800-53 Rev. 5 - SC-18: Outlines secure access control enforcement

Summary:
The scan likely flagged overly permissive or missing CORS headers. To address this securely, the analyst should configure the Access-Control-Allow-Origin header to limit access only to authorized, trusted domains. Let me kn

Explanation:

The question asks for the most efficient scanning technique to assess systems in a highly segmented network while minimizing the number of unique firewall rules, as part of deploying new vulnerability scanning software. Deploying agents on all systems is the most efficient approach, as it allows scans to occur locally on each system without requiring network traffic to traverse segmented boundaries, thus minimizing the need for firewall rule changes. This aligns with the CS0-003 exam’s Vulnerability Management (Domain 2) and Security Operations (Domain 1) objectives, which emphasize efficient vulnerability scanning and network security configuration.

Why A is Correct:

Local Scanning: Agent-based scanning installs lightweight software on each system (e.g., endpoints, servers) to perform vulnerability scans locally. Results are sent to a central management server over a single, standardized protocol (e.g., HTTPS), requiring minimal firewall rules (e.g., one rule to allow outbound communication to the server).

Minimized Firewall Rules: Since scans occur on the host itself, no additional rules are needed for scan traffic to cross network segments, addressing the networking team’s goal of minimizing unique firewall rules in a highly segmented network.

Cross-Segment Efficiency: Agents work independently of network segmentation, as they don’t rely on external scanners reaching each segment, making them ideal for complex, segmented environments.

CS0-003 Alignment: Agent-based scanning supports comprehensive vulnerability assessments (Domain 2) and aligns with secure network operations (Domain 1) by reducing network exposure and simplifying firewall configurations.

Why Other Options Are Wrong:

B. Deploy a central scanner and perform non-credentialed scans

Reason: A central scanner requires network access to all systems across the segmented network to perform scans, necessitating multiple firewall rules to allow scan traffic (e.g., TCP/UDP ports for protocols like SMB, SSH, or SNMP) between the scanner and each segment. Non-credentialed scans rely on network probes, which are less accurate and still require extensive firewall rule configurations to reach all systems, conflicting with the goal of minimizing rules. This approach is inefficient in a highly segmented network due to the increased rule complexity.

C. Deploy a cloud-based scanner and perform a network scan

Reason: A cloud-based scanner operates externally, requiring inbound access to all systems or a VPN/gateway setup, which demands multiple firewall rules to allow scan traffic into each network segment. Network scans from the cloud are typically non-credentialed, offering limited visibility into system vulnerabilities and requiring open ports (e.g., 445, 22) across segments, significantly increasing the number of firewall rules. This approach is impractical for minimizing firewall changes in a segmented network.

D. Deploy a scanner sensor on every segment and perform credentialed scans

Reason: Deploying a scanner sensor in each network segment allows credentialed scans, which are more accurate, but requires configuring firewall rules for each sensor to communicate with systems within its segment and back to a central management server. In a highly segmented network, this could result in numerous rules (e.g., one per segment for scan traffic and management traffic), failing to minimize unique firewall rules. The overhead of deploying and maintaining sensors in every segment also reduces efficiency compared to agent-based scanning.

Additional Context:

Agent-Based Scanning: Tools like Tenable Nessus Agents, Qualys Cloud Agents, or Rapid7 InsightVM agents perform local scans and report results to a central server, typically over a single port (e.g., 443). This reduces firewall complexity, as only outbound rules are needed, regardless of network segmentation.

Segmented Network Challenge: Highly segmented networks use VLANs, firewalls, or subnets to isolate systems, making centralized or external scanning difficult due to the need for multiple rules to allow scan traffic across boundaries. CS0-003 Relevance:The exam tests vulnerability scanning strategies, including selecting tools and techniques that balance accuracy, efficiency, and network security. Agent-based scanning is a common recommendation for complex environments.

Reference:

CompTIA CySA+ (CS0-003) Exam Objectives, Domains 1 (Security Operations) and 2 (Vulnerability Management),covering vulnerability scanning techniques and network security considerations.

CompTIA CySA+ Study Guide: Exam CS0-003 by Chapple and Seidl, discussing agent-based vs. network-based scanning and firewall rule management.

Explanation:

The question describes unusual network scanning activity originating from a foreign country where the company does not conduct any business. This makes the traffic both unsolicited and suspicious.

The best mitigation is to geoblock (geographically block) traffic from that entire country, which helps to: Proactively reduce attack surface from high-risk or irrelevant geolocations.

Eliminate future scans or attacks from the region.

Reduce the need for manual, ongoing IP-based blocking.

Since the company has no reason to accept traffic from that country, geoblocking is a clean, efficient, and effective solution.

Reference:
CompTIA CySA+ CS0-003 Objective 3.1 – Apply security solutions for infrastructure managem

NIST SP 800-41 Rev. 1 – Guidelines on Firewalls and Firewall Policy.

OWASP Security Logging and Monitoring suggests geolocation-based controls for anomalous traffic patterns.

Why the other options are less effective:

Block the IP range of the scans at the network firewall:

This could help, but attackers often rotate IPs or come from large, dynamic cloud blocks. It's less scalable than geoblocking.

Perform a historical trend analysis and look for similar scanning activity:

Good for investigation, but it’s passive, not a mitigation.

Block the specific IP address of the scans at the network firewall:

This is too narrow; attackers frequently change IPs, making this approach ineffective over time.

Summary:

Since the company does not interact with the country in question, geoblocking the entire region is the most efficient and effective mitigation technique to stop ongoing and future suspicious scanning activity Ask ChatGPT

Explanation:

The scenario mentions that the employee is no longer able to log in after a browser update, and they typically have several tabs open. This hints at a possible attack that abuses the user’s existing session or login state across browser tabs — which is typical of a CSRF attack.

Why CSRF is the most likely attack:

Cross-Site Request Forgery (CSRF) tricks a logged-in user’s browser into making unauthorized actions (like changing passwords, updating settings, or logging out) on a website where the user is already authenticated.

If the employee had multiple tabs open and was logged in to a target application, a malicious site in another tab could have issued unauthorized requests using their session.

After a browser update, cookies or sessions may have been invalidated or changed, preventing the CSRF attack from working again, which might explain why the employee is now logged out or cannot log in.

CSRF often goes unnoticed until after damage is done — for example, a password change or logout request silently sent in the background.

Reference:

OWASP CSRF Cheat Sheet
CompTIA CySA+ CS0-003 Objective 1.2 – Explain the relationship between security concepts and their role in IT security.

Why the other options are incorrect:

A. RFI (Remote File Inclusion):
Involves including remote files via input fields or URLs — a server-side code injection, not related to login or browser behavior.

B. LFI (Local File Inclusion):
Similar to RFI, but includes files already present on the server. Again, this is server-side exploitation, not session abuse across tabs.

D. XSS (Cross-Site Scripting):
Can also execute malicious scripts in the browser, but typically shows visible signs (popups, redirects).

It’s more about stealing data or injecting code — less likely to log someone out silently or affect session state like CSRF.

Summary:

The most likely attack is CSRF, since it exploits the user's browser session across tabs to perform actions without their consent, aligning closely with the behavior described in the scenario. Ask ChatGPT

Explanation:

The vulnerability scan revealed an issue exploitable over port 3389, which is commonly used for Remote Desktop Protocol (RDP) — not web services. The key points in the scenario are:

The vulnerable host is a web server in the perimeter network (i.e., externally accessible).

The system is protected by a Web Application Firewall (WAF).

The vulnerability affects port 3389 (RDP) — not web traffic.

Why the correct answer is: "The risk would increase because the host is external facing":

Because the host is accessible from the internet, any vulnerability exposed on an open port like 3389 represents a higher risk:

External exposure means attackers worldwide can attempt to exploit the vulnerability.

RDP has a long history of critical vulnerabilities and brute-force attacks.

A WAF only protects web-layer (HTTP/HTTPS) traffic, not RDP, so the vulnerability on port 3389 is not mitigated by the WAF.

As a result, having an unprotected, exploitable port open to the internet increases the likelihood of compromise, which increases the overall risk.

Reference:

NIST SP 800-30 Rev. 1 – Risk Assessment Guide for Information Technology Systems

NIST SP 800-30 Rev. 1 – Risk Assessment Guide for Information Technology Systems

Why the other options are incorrect:

"The risk would not change because network firewalls are in use":

If firewalls were effectively blocking RDP, it wouldn’t have shown up as exploitable in the scan. So, either firewalls aren't configured properly, or port 3389 is open — meaning risk is not neutralized.

"The risk would decrease because RDP is blocked by the firewall": The question doesn’t state that RDP is blocked. In fact, the scan found it vulnerable, suggesting it is open and reachable.
"The risk would decrease because a web application firewall is in place": A WAF only protects web applications (typically on ports 80/443), not RDP. Therefore, it does not reduce risk on port 3389.
Summary:

An external-facing host with a vulnerability on port 3389 poses increased risk, regardless of WAF protection, because the exposure to the public internet greatly increases the likelihood of attack — making "The risk would increase because the host is external facing" the correct and most complete answer.

Explanation:

The CISO's after-action report highlights a human error issue: employees using legacy applications struggle to distinguish between phishing and legitimate emails. This is a user awareness problem, not a technical flaw in the applications themselves.

The most appropriate and direct remediation is to provide targeted security awareness training and education. This would: Teach employees how to recognize phishing indicators (e.g., suspicious links, urgent language, spoofed sender addresses). Improve user decision-making and reduce risk of email-based attacks like credential theft or malware execution. Possibly include phishing simulations and ongoing training to build resilience over time.

Reference:

NIST SP 800-50 – Building an Information Technology Security Awareness and Training Program

NIST SP 800-50 – Building an Information Technology Security Awareness and Training Program

Why the other options are incorrect:

Replacement of legacy applications:

While modern apps may have better built-in security, the issue here is user behavior, not the software itself. Replacing apps wouldn’t solve poor phishing recognition.

Organizational governance:

This refers to policies, frameworks, and oversight. It's important but too high-level and indirect to address a specific knowledge gap.

Multifactor authentication on all systems:

MFA helps mitigate the impact of phishing, but it doesn’t solve the root problem of employees being unable to recognize phishing emails. It’s a technical control, not a user-focused remedy.

Summary:

Because the core issue is lack of employee awareness and ability to recognize phishing, the most effective action plan item is security awareness training and education — making it the best and most targeted choice.

Explanation:

The threat intelligence describes an actor with “seemingly unlimited time and resources.” This strongly indicates a nation-state threat actor.

Nation-state attackers are typically:

Backed by governments, giving them access to extensive funding, skilled personnel, and intelligence capabilities.

Able to conduct long-term, stealthy, and sophisticated operations, often targeting critical infrastructure, government systems, intellectual property, or political objectives.

Known to use zero-day exploits, custom malware, and advanced persistent threats (APTs).

Less concerned with speed and more focused on strategic objectives.

Reference:

NIST SP 800-30 Rev. 1 – Describes nation-state actors as having advanced capabilities and long-term persistence.

MITRE ATT&CK® – Classifies several threat groups (e.g., APT29, APT28) as nation-state-sponsored actors.

Why the other options are incorrect:

Insider threat:

Comes from someone within the organization (employee, contractor). These threats are localized and resource-limited, not aligned with “unlimited time and resources.”

Ransomware group:

Typically financially motivated and operates more opportunistically, not persistently or with nation-level backing. They aim for quick payouts, not strategic espionage.

Organized crime:

These actors can be well-funded but are still resource-constrained compared to a nation-state. Their goals are usually financial, not geopolitical or strategic.

Summary:

When threat intelligence mentions an actor with unlimited time and resources, the most accurate classification is a nation-state actor, due to the strategic motivation and government-level backing involved. Ask ChatGPT

Explanation:

The question asks for the best method to protect the confidentiality of Personally Identifiable Information (PII) data records when importing them from a production environment to a test environment. Data masking is the most effective solution, as it obscures sensitive data (e.g., PII) while preserving its format and usability for testing, ensuring confidentiality. This aligns with the CS0-003 exam’s Security Operations (Domain 1) and Reporting and Communication (Domain 4) objectives, which emphasize protecting sensitive data and implementing secure data handling practices.

Why A is Correct:

Data Masking Overview: Data masking replaces sensitive data (e.g., names, Social Security numbers, credit card numbers) with realistic but fictitious values, maintaining the data’s structure and functionality for testing without exposing actual PII. For example, “John Doe” might become “Jane Smith,” or “123-45-6789” might become “987-65-4321.”

Confidentiality Protection: By altering PII, data masking ensures that even if the test environment is compromised, the exposed data is not real, safeguarding confidentiality.

Test Environment Suitability: Masked data retains the format needed for testing (e.g., valid field lengths or data types), allowing developers to test applications without accessing actual PII.

CS0-003 Alignment: The exam emphasizes secure data handling practices, including protecting PII during data transfers or testing, making data masking a standard approach for compliance with regulations like GDPR or HIPAA.

Why Other Options Are Wrong:

B. Hashing
Reason: Hashing transforms data into a fixed-length, irreversible value (e.g., SHA-256 hash) using a one-way function. While hashing protects data integrity and is useful for password storage, it renders data unusable for testing because the original format (e.g., a readable name or phone number) is lost. Test environments require data that mimics production data’s structure, which hashing cannot provide, making it unsuitable for this scenario.

C. Watermarking
Reason: Watermarking embeds identifiable markers into data (e.g., a digital signature or visible overlay) to track its origin or detect unauthorized use. It does not obscure or encrypt PII, so it fails to protect confidentiality. If a watermarked PII record is exposed in the test environment, the actual sensitive data remains at risk, making this option ineffective for the stated goal.

D. Encoding
Reason: Encoding (e.g., Base64) converts data into a different representation for transmission or storage but is easily reversible (e.g., decoding Base64 restores the original data). It provides no confidentiality, as anyone with access to the test environment can decode the PII, exposing sensitive information. Encoding is not a security measure and doesn’t meet the requirement to protect data confidentiality.

Additional Context:

PII and Test Environments: PII (e.g., names, addresses, SSNs) requires strict protection under regulations like GDPR, HIPAA, or CCPA. Importing unmasked PII into a test environment risks breaches, especially if the test environment is less secure than production.

Data Masking Techniques: Common methods include substitution (replacing data with fake values), shuffling, or anonymization, ensuring the data remains functional for testing. Tools like Informatica or Delphix support data masking for compliance.

CS0-003 Relevance: The exam tests secure data handling and risk mitigation, including protecting sensitive data during transfers or testing (Domain 1) and communicating compliance requirements (Domain 4).

Reference:

CompTIA CySA+ (CS0-003) Exam Objectives, Domains 1 (Security Operations) and 4 (Reporting and Communication),covering secure data handling and PII protection. CompTIA CySA+ Study Guide: Exam CS0-003 by Chapple and Seidl, discussing data masking as a best practice for protecting sensitive data in non-production environments.

Explanation:

This question tests your ability to compare CVSS v3.1 base scores to determine risk impact, especially under remediation constraints

The goal is to identify the least impactful vulnerability — the one with the lowest overall risk — so it can be deferred.

CVSS v3.1 Base Score Overview:

The Common Vulnerability Scoring System (CVSS) uses the following vectors:

AV (Attack Vector) – How remote the attack can be.

AC (Attack Complexity) – How difficult it is to exploit.

PR (Privileges Required) – Level of access needed.

UI (User Interaction) – Whether user input is needed.

S (Scope) – Whether other systems or components are affected.

C/I/A (Confidentiality, Integrity, Availability impact) – Degree of impact (None, Low, High).

Why Option A (Base Score 6.0) is Least Impactful:

Vector Breakdown: AV:N – Network (can be exploited remotely)

AC:H – High complexity (makes exploitation difficult)

PR:H – High privileges required (attacker must already be privileged)

UI:R – Requires user interaction

S:U – Scope is unchanged (limited to the same component)

C:H/I:H/A:L – High confidentiality & integrity impact, low availability impact

Despite high C and I impact, the high attack complexity, high privileges required, and required user interaction make exploitation unlikely in real-world terms.

Comparison to Other Options:

Option B (7.2) – Has scope changed (S:C) and no user interaction, so it's more impactful.

Option C (6.4) – Similar to A, but higher availability impact, so more risk.

Option D (6.5) – Requires no privileges and no user interaction, making it easier to exploit despite low impact values.

Summary:

The lowest-risk option — considering both CVSS score and exploit conditions — is:

AV:N/AC:H/PR:H/UI:R/S:U/C:H/I:H/A:L — Base Score 6.0

This is the least impactful risk and can be safely deprioritized for remediation this sprint

Reference:

CVSS v3.1 Specification

CompTIA CySA+ CS0-003 Objective 2.5 – Interpret the output from vulnerability scans.