- A
Enable Windows Defender Firewall on each workstation
Why wrong: Firewall controls inbound/outbound traffic but does not filter by website reputation.
- B
Configure a DNS filtering service on the router or DNS server
DNS filtering resolves malicious domains to a block page, preventing access at the network level.
- C
Install a browser extension on all computers
Why wrong: Browser extensions require installation on each client and can be bypassed by users.
- D
Set the browser security level to high
Why wrong: High security settings may block some content but do not filter by known malicious sites.
Question 239 of 750
How to Use DNS Filtering to Block Malicious Sites
This 220-1202 practice question tests your understanding of browser and application security. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company policy requires that all web traffic be filtered to block known malicious sites. You need to implement this on the network without installing software on each client. What should you configure?
Quick Answer
The answer is to configure a DNS filtering service on the router or DNS server. This is correct because DNS filtering operates at the network level, intercepting DNS queries and blocking resolution for known malicious domains before any traffic reaches the client, which satisfies the policy requirement of no client-side software installation. On the CompTIA A+ Core 2 220-1202 exam, this question tests your understanding of network-based security implementations versus host-based solutions like antivirus or browser extensions. A common trap is choosing a client-side firewall or proxy configuration that requires per-machine setup, which violates the "without installing software" constraint. Remember the key distinction: DNS filtering is a server-side or router-level control that blocks by domain name, not by IP address. For a quick memory tip, think "DNS = Domain Name Stop" — the filter stops the lookup before the connection starts.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure a DNS filtering service on the router or DNS server
A DNS filtering service works at the network level by resolving domain names against a blocklist of known malicious sites. By configuring this on the router or DNS server, all client traffic is filtered transparently without requiring any software installation on individual workstations, which satisfies the policy requirement.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Enable Windows Defender Firewall on each workstation
Why it's wrong here
Firewall controls inbound/outbound traffic but does not filter by website reputation.
- ✓
Configure a DNS filtering service on the router or DNS server
Why this is correct
DNS filtering resolves malicious domains to a block page, preventing access at the network level.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Install a browser extension on all computers
Why it's wrong here
Browser extensions require installation on each client and can be bypassed by users.
- ✗
Set the browser security level to high
Why it's wrong here
High security settings may block some content but do not filter by known malicious sites.
Common exam traps
Common exam trap: answer the scenario, not the keyword
A common trap on the CompTIA A+ exam is confusing host-based and network-based security controls. Candidates may choose a host-based solution (like firewall or browser settings) instead of recognizing that DNS filtering is a network-level, agentless method that meets the 'no client software' constraint.
Detailed technical explanation
How to think about this question
DNS filtering typically uses a DNS forwarder or resolver that queries a threat-intelligence feed (e.g., from Cisco Umbrella or Quad9) and returns a null IP (0.0.0.0) or a sinkhole IP for blocked domains. This approach leverages the DNS protocol (RFC 1035) and can be implemented via a local DNS server or router-level DNS settings, ensuring all HTTP/HTTPS traffic to blocked domains fails at the name resolution stage before any connection is attempted.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 220-1202 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Visual reference
What to study next
Got this wrong? Here's your next step.
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Browser and Application Security — study guide chapter
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FAQ
Questions learners often ask
What does this 220-1202 question test?
Browser and Application Security — This question tests Browser and Application Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure a DNS filtering service on the router or DNS server — A DNS filtering service works at the network level by resolving domain names against a blocklist of known malicious sites. By configuring this on the router or DNS server, all client traffic is filtered transparently without requiring any software installation on individual workstations, which satisfies the policy requirement.
What should I do if I get this 220-1202 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
This 220-1202 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 220-1202 exam.
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