Network Security Groups (NSG) in Azure - Mini Project: Build & Apply

Network Security Groups (NSG) Setup in Azure

📖 Scenario: You are setting up a simple network security group (NSG) in Azure to control traffic to a virtual machine. This NSG will allow HTTP traffic and block all other inbound traffic by default.

🎯 Goal: Create an Azure Network Security Group (NSG) with a rule that allows inbound HTTP traffic on port 80 and denies all other inbound traffic.

📋 What You'll Learn

Create a Network Security Group resource named myNSG.

Add a security rule named AllowHTTP that allows inbound TCP traffic on port 80.

Set the priority of AllowHTTP rule to 100.

Ensure the default inbound rule denies all other inbound traffic.

💡 Why This Matters

🌍 Real World

Network Security Groups are used in Azure to control inbound and outbound traffic to resources like virtual machines, improving security by allowing only necessary traffic.

💼 Career

Understanding NSGs is essential for cloud engineers and network administrators to secure cloud infrastructure and comply with organizational security policies.

1

Create the Network Security Group resource

Create an Azure Network Security Group resource named myNSG with location eastus and an empty securityRules list.

Azure

# Create the NSG resource with name 'myNSG' and location 'eastus'
# Your code here

Hint

Use the Azure resource type Microsoft.Network/networkSecurityGroups and set securityRules to an empty list.

2

Add a security rule to allow HTTP inbound traffic

Add a security rule named AllowHTTP inside the securityRules list of myNSG. This rule should allow inbound TCP traffic on port 80 with priority 100 and direction Inbound.

Azure

{
  "type": "Microsoft.Network/networkSecurityGroups",
  "apiVersion": "2022-05-01",
  "name": "myNSG",
  "location": "eastus",
  "properties": {
    "securityRules": [
      {
        // Add the AllowHTTP rule here
      }
    ]
  }
}

Hint

Define the rule with name, priority, protocol, access, direction, and port ranges.

3

Add a default deny inbound rule

Add a security rule named DenyAllInbound with priority 4096 that denies all inbound traffic. Place this rule inside the securityRules list after the AllowHTTP rule.

Azure

{
  "type": "Microsoft.Network/networkSecurityGroups",
  "apiVersion": "2022-05-01",
  "name": "myNSG",
  "location": "eastus",
  "properties": {
    "securityRules": [
      {
        "name": "AllowHTTP",
        "properties": {
          "priority": 100,
          "protocol": "Tcp",
          "access": "Allow",
          "direction": "Inbound",
          "sourceAddressPrefix": "*",
          "sourcePortRange": "*",
          "destinationAddressPrefix": "*",
          "destinationPortRange": "80"
        }
      },
      {
        // Add DenyAllInbound rule here
      }
    ]
  }
}

Hint

The deny rule should block all protocols and ports with a high priority number.

4

Complete the NSG configuration

Ensure the entire Network Security Group JSON includes both AllowHTTP and DenyAllInbound rules inside the securityRules list under properties. The NSG name must be myNSG and location eastus.

Azure

{
  // Verify the full NSG JSON includes both rules and correct name and location
  // Your code here
}

Hint

Double-check the NSG name, location, and that both rules are present in the securityRules list.

Practice

1. What is the primary purpose of an Azure Network Security Group (NSG)?

easy

A. To monitor application performance

B. To store data securely in Azure Blob Storage

C. To control inbound and outbound traffic to Azure resources

D. To manage user identities and access

Solution

1. Step 1: Understand NSG function

   NSGs are designed to filter network traffic to and from Azure resources.

2. Step 2: Identify correct purpose

   They do not store data, manage identities, or monitor performance.

3. Final Answer:

   To control inbound and outbound traffic to Azure resources -> Option C

4. Quick Check:

   NSG controls traffic [OK]

Hint: NSG controls network traffic, not data or users [OK]

Common Mistakes:

• Confusing NSG with storage or identity services
• Thinking NSG monitors performance
• Assuming NSG stores data

2. Which of the following is the correct way to specify a rule priority in an NSG rule?

easy

A. Priority is a string describing the rule

B. Priority is an IP address range

C. Priority is a boolean value true or false

D. Priority must be a unique integer between 100 and 4096

Solution

1. Step 1: Understand NSG rule priority format

   NSG rule priority is a unique integer between 100 and 4096 that determines rule evaluation order.

2. Step 2: Eliminate incorrect types

   Priority is not a string, boolean, or IP range.

3. Final Answer:

   Priority must be a unique integer between 100 and 4096 -> Option D

4. Quick Check:

   Priority = integer 100-4096 [OK]

Hint: Priority is a number from 100 to 4096 [OK]

Common Mistakes:

• Using strings or booleans for priority
• Confusing priority with IP ranges
• Not using unique priority numbers

3. Given this NSG rule:
Priority: 200, Direction: Inbound, Access: Deny, Source: Any, Destination: 10.0.0.4, Protocol: TCP, Port: 22
What happens when a user tries to SSH (port 22) to 10.0.0.4?

medium

A. The connection is denied

B. The connection is allowed only if from a specific IP

C. The connection is allowed

D. The connection is logged but allowed

Solution

1. Step 1: Analyze rule details

   The rule denies inbound TCP traffic on port 22 to destination 10.0.0.4 from any source.

2. Step 2: Determine effect on SSH connection

   SSH uses TCP port 22, so the connection attempt matches the deny rule and is blocked.

3. Final Answer:

   The connection is denied -> Option A

4. Quick Check:

   Deny inbound TCP port 22 = connection denied [OK]

Hint: Deny inbound on port 22 blocks SSH connections [OK]

Common Mistakes:

• Assuming 'Any' source means allow
• Confusing deny with logging
• Ignoring direction and port in rule

4. You created an NSG rule to allow inbound HTTP traffic on port 80, but the traffic is still blocked. What is the most likely cause?

medium

A. The NSG is not attached to the subnet or network interface

B. A higher priority deny rule blocks port 80 traffic

C. The source IP address is not specified

D. The protocol is set to UDP instead of TCP

Solution

1. Step 1: Check rule priority and conflicts

   NSG rules are evaluated by priority; a deny rule with higher priority can block traffic despite allow rules.

2. Step 2: Confirm rule attachment and protocol

   While attachment and protocol matter, the most common cause is a conflicting higher priority deny rule.

3. Final Answer:

   A higher priority deny rule blocks port 80 traffic -> Option B

4. Quick Check:

   Higher priority deny overrides allow [OK]

Hint: Check for higher priority deny rules first [OK]

Common Mistakes:

• Ignoring rule priority order
• Assuming NSG attachment is always correct
• Confusing protocol types

5. You want to restrict access so only a specific IP address (203.0.113.5) can access a VM on port 3389 (RDP). Which NSG rule configuration achieves this securely?

hard

A. Priority: 300, Direction: Inbound, Access: Allow, Source: 203.0.113.5, Destination: Any, Protocol: TCP, Port: 3389

B. Priority: 100, Direction: Inbound, Access: Deny, Source: Any, Destination: Any, Protocol: TCP, Port: 3389

C. Priority: 200, Direction: Inbound, Access: Allow, Source: Any, Destination: Any, Protocol: TCP, Port: 3389

D. Priority: 400, Direction: Outbound, Access: Allow, Source: 203.0.113.5, Destination: Any, Protocol: TCP, Port: 3389

Solution

1. Step 1: Allow only specific IP inbound on port 3389

   Priority: 300, Direction: Inbound, Access: Allow, Source: 203.0.113.5, Destination: Any, Protocol: TCP, Port: 3389 allows inbound TCP traffic on port 3389 only from IP 203.0.113.5, which matches the requirement.

2. Step 2: Check other options for correctness

   Priority: 100, Direction: Inbound, Access: Deny, Source: Any, Destination: Any, Protocol: TCP, Port: 3389 denies all inbound TCP 3389 traffic, blocking access. Priority: 200, Direction: Inbound, Access: Allow, Source: Any, Destination: Any, Protocol: TCP, Port: 3389 allows all sources, which is insecure. Priority: 400, Direction: Outbound, Access: Allow, Source: 203.0.113.5, Destination: Any, Protocol: TCP, Port: 3389 is outbound, irrelevant for inbound access.

3. Final Answer:

   Priority: 300, Direction: Inbound, Access: Allow, Source: 203.0.113.5, Destination: Any, Protocol: TCP, Port: 3389 -> Option A

4. Quick Check:

   Allow inbound TCP 3389 from specific IP [OK]

Hint: Allow inbound from specific IP, deny others by priority [OK]

Common Mistakes:

• Allowing all sources instead of specific IP
• Using outbound direction instead of inbound
• Denying all traffic without exception