Azure Firewall Rule Not Blocking Tor Exit Nodes? Check Destination Port Configuration
This SC-200 practice question tests your understanding of manage a security operations environment. 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.
Exhibit
Refer to the exhibit.
```json
{
"properties": {
"displayName": "Block Tor IPs",
"description": "Blocks traffic from known Tor exit nodes.",
"ruleType": "Prevention",
"action": "Block",
"priority": 100,
"sourceAddress": ["138.197.0.0/16", "104.131.0.0/16"],
"destinationAddress": ["*"],
"sourcePorts": ["*"],
"destinationPorts": ["443", "80"],
"protocol": "TCP",
"direction": "Inbound"
}
}
```
You are a security analyst for a company that uses Azure Firewall. You are reviewing a custom rule deployed via Azure Firewall Manager. The exhibit shows the rule configuration. The rule is intended to block inbound traffic from known Tor exit nodes. However, a recent incident involved an attacker using a Tor exit node with IP 138.197.5.5 to access an internal web server on port 8080. The log shows the traffic was ALLOWED. What is the most likely reason the rule did not block the traffic?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Exhibit
Refer to the exhibit.
```json
{
"properties": {
"displayName": "Block Tor IPs",
"description": "Blocks traffic from known Tor exit nodes.",
"ruleType": "Prevention",
"action": "Block",
"priority": 100,
"sourceAddress": ["138.197.0.0/16", "104.131.0.0/16"],
"destinationAddress": ["*"],
"sourcePorts": ["*"],
"destinationPorts": ["443", "80"],
"protocol": "TCP",
"direction": "Inbound"
}
}
```
A
The destination port 8080 is not listed in the rule.
The rule only blocks ports 443 and 80, but the traffic used port 8080.
B
The source address range does not include 138.197.5.5.
Why wrong: The source address includes 138.197.0.0/16, which covers 138.197.5.5.
C
The rule type is 'Prevention' but should be 'Detection'.
Why wrong: Rule type Prevention is correct for blocking; Detection would only log.
D
The rule priority is too low and is overridden by a higher priority rule.
Why wrong: Priority 100 is numeric; lower number means higher priority. 100 is relatively high priority (i.e., evaluated sooner), but even if overridden, the rule would still be evaluated for matching ports.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The destination port 8080 is not listed in the rule.
Option A is correct because the rule is configured to block traffic on destination port 80, but the attacker used port 8080. Azure Firewall rules are explicit; if the destination port in the traffic does not match any port specified in the rule, the rule is not applied, and the traffic is evaluated by subsequent rules or default allow logic. Since the rule only lists port 80, traffic to port 8080 is not matched, and thus the rule does not block it.
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.
✓
The destination port 8080 is not listed in the rule.
Why this is correct
The rule only blocks ports 443 and 80, but the traffic used port 8080.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The source address range does not include 138.197.5.5.
Why it's wrong here
The source address includes 138.197.0.0/16, which covers 138.197.5.5.
✗
The rule type is 'Prevention' but should be 'Detection'.
Why it's wrong here
Rule type Prevention is correct for blocking; Detection would only log.
✗
The rule priority is too low and is overridden by a higher priority rule.
Why it's wrong here
Priority 100 is numeric; lower number means higher priority. 100 is relatively high priority (i.e., evaluated sooner), but even if overridden, the rule would still be evaluated for matching ports.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume a rule blocking a source IP will block all traffic from that IP, but Azure Firewall rules require exact port matching, and the rule only specifies port 80, not port 8080.
Detailed technical explanation
How to think about this question
Azure Firewall rules are stateless for network rules and stateful for application rules, but custom DNAT or network rules require exact matches on source, destination, port, and protocol. If any field does not match, the rule is not applied, and the firewall falls through to the next rule or default behavior (typically allow for outbound, deny for inbound unless overridden). In this scenario, the rule's destination port list (80) is a single value, not a range or wildcard, so traffic to port 8080 is not matched. A common real-world mistake is assuming a rule blocks all traffic from a source IP regardless of port, but Azure Firewall requires explicit port matching.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this SC-200 question in full detail.
Manage a security operations environment — This question tests Manage a security operations environment — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The destination port 8080 is not listed in the rule. — Option A is correct because the rule is configured to block traffic on destination port 80, but the attacker used port 8080. Azure Firewall rules are explicit; if the destination port in the traffic does not match any port specified in the rule, the rule is not applied, and the traffic is evaluated by subsequent rules or default allow logic. Since the rule only lists port 80, traffic to port 8080 is not matched, and thus the rule does not block it.
What should I do if I get this SC-200 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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