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Design security solutions for infrastructure →hardMultiple ChoiceObjective-mapped

Quick Answer

The correct answer is that the ARM template NSG rule is overly permissive because it allows inbound HTTPS traffic from any Internet source to the subnet 10.0.1.0/24. This configuration creates a security risk by exposing the frontend subnet to the entire internet without restricting source IP addresses, effectively bypassing the principle of least privilege. On the Microsoft Cybersecurity Architect exam, this scenario tests your ability to identify misconfigured network security groups in ARM templates, a common trap where candidates overlook the "Any" source property and focus only on the port or protocol. The key distinction is that an NSG rule permitting HTTPS (port 443) from the Internet to a subnet is not inherently wrong—it becomes a vulnerability only when the source is unrestricted. A useful memory tip: "Any source on 443 means the whole world is at your door."

SC-100 Design security solutions for infrastructure Practice Question

This SC-100 practice question tests your understanding of design security solutions for infrastructure. 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

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {},
  "resources": [
    {
      "type": "Microsoft.Network/networkSecurityGroups",
      "apiVersion": "2020-06-01",
      "name": "nsg-frontend",
      "properties": {
        "securityRules": [
          {
            "name": "AllowHTTPS",
            "properties": {
              "protocol": "Tcp",
              "sourcePortRange": "*",
              "destinationPortRange": "443",
              "sourceAddressPrefix": "Internet",
              "destinationAddressPrefix": "10.0.1.0/24",
              "access": "Allow",
              "priority": 100,
              "direction": "Inbound"
            }
          }
        ]
      }
    }
  ]
}

Refer to the exhibit. You are deploying an ARM template for a network security group. What is the security implication of this configuration?

Question 1hardmultiple choice
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Exhibit

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {},
  "resources": [
    {
      "type": "Microsoft.Network/networkSecurityGroups",
      "apiVersion": "2020-06-01",
      "name": "nsg-frontend",
      "properties": {
        "securityRules": [
          {
            "name": "AllowHTTPS",
            "properties": {
              "protocol": "Tcp",
              "sourcePortRange": "*",
              "destinationPortRange": "443",
              "sourceAddressPrefix": "Internet",
              "destinationAddressPrefix": "10.0.1.0/24",
              "access": "Allow",
              "priority": 100,
              "direction": "Inbound"
            }
          }
        ]
      }
    }
  ]
}

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

✓

The rule allows inbound HTTPS traffic from any Internet source to the subnet, which may be overly permissive

Option C is correct because the rule allows HTTPS from the Internet to the subnet 10.0.1.0/24, making the frontend accessible from anywhere, which is a security risk if not intended. Option A is wrong because the rule does allow Internet traffic. Option B is wrong because the rule is inbound, not outbound. Option D is wrong because the rule allows traffic on port 443.

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.

  • ✗

    The rule only allows traffic on port 443 from a specific IP range

    Why it's wrong here

    The sourceAddressPrefix is 'Internet', not a specific range.

  • ✗

    The rule allows outbound traffic from the subnet to the Internet

    Why it's wrong here

    The rule is inbound, not outbound.

  • ✓

    The rule allows inbound HTTPS traffic from any Internet source to the subnet, which may be overly permissive

    Why this is correct

    Allowing Internet access to a subnet without restrictions is a security concern.

    Related concept

    CIDR notation defines the prefix length.

  • ✗

    The rule blocks all inbound traffic from the Internet

    Why it's wrong here

    The rule allows inbound traffic from Internet.

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.

What to study next

Got this wrong? Here's your next step.

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-100 subnetting questions on CIDR, address ranges, and subnet selection.

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FAQ

Questions learners often ask

What does this SC-100 question test?

Design security solutions for infrastructure — This question tests Design security solutions for infrastructure — CIDR notation defines the prefix length..

What is the correct answer to this question?

The correct answer is: The rule allows inbound HTTPS traffic from any Internet source to the subnet, which may be overly permissive — Option C is correct because the rule allows HTTPS from the Internet to the subnet 10.0.1.0/24, making the frontend accessible from anywhere, which is a security risk if not intended. Option A is wrong because the rule does allow Internet traffic. Option B is wrong because the rule is inbound, not outbound. Option D is wrong because the rule allows traffic on port 443.

What should I do if I get this SC-100 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-100 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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Last reviewed: Jun 21, 2026

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