The answer is that this rule blocks inbound SMB traffic from the internet to the subnet. This is correct because the security admin rule denies inbound TCP traffic on port 445, which is the default port for Server Message Block (SMB) protocol, targeting the subnet 10.0.0.0/24 from the Internet source. In Azure Virtual Network Manager, security admin rules enforce network-wide policies, and this specific configuration prevents external SMB access, a common vector for ransomware propagation. On the SC-900 exam, this tests your ability to interpret Azure Virtual Network Manager security admin rules and map port numbers to protocols, often appearing in scenario-based questions with an exhibit. A common trap is confusing port 445 with RDP (3389) or misreading the direction as outbound. Remember the mnemonic: “SMB 445, deny from outside to stay alive.”
SC-900 Practice Question: Describe the capabilities of Microsoft security solutions
This SC-900 practice question tests your understanding of describe the capabilities of microsoft security solutions. 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.
Refer to the exhibit. You are a security administrator for a company using Azure Virtual Network Manager. You have deployed the security admin configuration shown. What is the impact of this rule?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
It blocks inbound SMB traffic from the internet to the subnet.
The rule denies inbound TCP traffic on port 445 (SMB) from the Internet to the subnet 10.0.0.0/24. This blocks external SMB access, preventing common ransomware propagation. Option A is incorrect because port 445 is SMB, not RDP (3389). Option C is incorrect because direction is inbound. Option D is incorrect because it denies all traffic only on port 445, not all ports.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
It blocks inbound SMB traffic from the internet to the subnet.
Why this is correct
SMB uses port 445; the rule denies internet-to-subnet traffic on that port.
It blocks outbound traffic from the subnet to the internet.
Why it's wrong here
The direction is Inbound, not Outbound.
✗
It denies all traffic from the internet to the subnet.
Why it's wrong here
Only traffic on port 445 is denied, not all ports.
✗
It blocks inbound RDP traffic from the internet.
Why it's wrong here
RDP uses port 3389, not 445.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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-900 question in full detail.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SC-900 subnetting questions on CIDR, address ranges, and subnet selection.
Describe the capabilities of Microsoft security solutions — This question tests Describe the capabilities of Microsoft security solutions — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: It blocks inbound SMB traffic from the internet to the subnet. — The rule denies inbound TCP traffic on port 445 (SMB) from the Internet to the subnet 10.0.0.0/24. This blocks external SMB access, preventing common ransomware propagation. Option A is incorrect because port 445 is SMB, not RDP (3389). Option C is incorrect because direction is inbound. Option D is incorrect because it denies all traffic only on port 445, not all ports.
What should I do if I get this SC-900 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SC-900 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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