Firewall and DMZ for SCADA in SCADA systems - Mini Project: Build & Apply

Firewall and DMZ for SCADA

📖 Scenario: You are working in a SCADA (Supervisory Control and Data Acquisition) environment that controls critical infrastructure. To protect the SCADA network from external threats, you need to set up a firewall and a DMZ (Demilitarized Zone). The DMZ will host servers that communicate with both the external network and the SCADA network, acting as a buffer zone.This project will guide you through creating a simple firewall rule set and defining the DMZ network segment in a configuration file format used by SCADA network devices.

🎯 Goal: Build a basic firewall configuration that defines the SCADA network, the DMZ network, and firewall rules to allow only specific traffic between them and the external network.

📋 What You'll Learn

Create a dictionary called networks with exact IP ranges for SCADA and DMZ

Add a variable called allowed_services listing the service ports allowed through the firewall

Create a list called firewall_rules that applies rules for traffic between networks using the allowed services

Print the firewall_rules list to show the final configuration

💡 Why This Matters

🌍 Real World

SCADA systems control critical infrastructure like power plants and water treatment. Protecting these systems with firewalls and DMZs helps prevent cyber attacks that could disrupt essential services.

💼 Career

Network and security engineers working with industrial control systems need to configure firewalls and DMZs to secure SCADA networks from unauthorized access.

1

Define SCADA and DMZ network IP ranges

Create a dictionary called networks with these exact entries: 'SCADA': '192.168.10.0/24' and 'DMZ': '192.168.20.0/24'.

SCADA systems

# Create the networks dictionary with SCADA and DMZ IP ranges
# Your code here

Hint

Use a Python dictionary with keys 'SCADA' and 'DMZ' and assign the exact IP ranges as strings.

2

List allowed service ports for firewall

Create a list called allowed_services with these exact port numbers as integers: 502 (Modbus), 80 (HTTP), and 443 (HTTPS).

SCADA systems

networks = {
    'SCADA': '192.168.10.0/24',
    'DMZ': '192.168.20.0/24'
}
# Create the allowed_services list with ports 502, 80, and 443
# Your code here

Hint

Use a Python list with the exact port numbers as integers.

3

Create firewall rules for SCADA and DMZ traffic

Create a list called firewall_rules that contains strings. Each string should be a rule allowing traffic from networks['DMZ'] to networks['SCADA'] on each port in allowed_services. Use a for loop with variables port to generate rules in the format: 'allow DMZ to SCADA on port {port}'.

SCADA systems

networks = {
    'SCADA': '192.168.10.0/24',
    'DMZ': '192.168.20.0/24'
}

allowed_services = [502, 80, 443]

# Create firewall_rules list with rules allowing DMZ to SCADA traffic on allowed_services ports
# Your code here

Hint

Use a for loop over allowed_services and append formatted strings to firewall_rules.

4

Display the firewall rules

Write a print statement to display the firewall_rules list.

SCADA systems

networks = {
    'SCADA': '192.168.10.0/24',
    'DMZ': '192.168.20.0/24'
}

allowed_services = [502, 80, 443]

firewall_rules = []
for port in allowed_services:
    firewall_rules.append(f'allow DMZ to SCADA on port {port}')

# Print the firewall_rules list
# Your code here

Hint

Use print(firewall_rules) to show the list of rules.

Practice

1. What is the main purpose of a firewall in a SCADA system?

easy

A. To control and filter network traffic to protect SCADA devices

B. To store data collected from SCADA sensors

C. To provide power backup for SCADA devices

D. To physically connect SCADA devices to the internet

Solution

1. Step 1: Understand firewall function

   A firewall acts like a gatekeeper that controls which data can enter or leave a network.

2. Step 2: Apply to SCADA context

   In SCADA, it filters traffic to protect sensitive control systems from unauthorized access.

3. Final Answer:

   To control and filter network traffic to protect SCADA devices -> Option A

4. Quick Check:

   Firewall controls traffic = C [OK]

Hint: Firewalls filter traffic to protect systems [OK]

Common Mistakes:

• Confusing firewall with data storage
• Thinking firewall provides power
• Assuming firewall connects devices physically

2. Which of the following is the correct way to describe a DMZ in SCADA networks?

easy

A. A network zone that directly connects SCADA devices to the internet

B. A backup power supply for SCADA control centers

C. A secure area that isolates SCADA devices from other networks

D. A software tool for monitoring SCADA device performance

Solution

1. Step 1: Define DMZ purpose

   A DMZ (Demilitarized Zone) is a network area that separates internal systems from external networks.

2. Step 2: Apply to SCADA

   It isolates SCADA devices to reduce risk from outside attacks while allowing controlled access.

3. Final Answer:

   A secure area that isolates SCADA devices from other networks -> Option C

4. Quick Check:

   DMZ isolates SCADA = B [OK]

Hint: DMZ isolates SCADA from other networks [OK]

Common Mistakes:

• Thinking DMZ connects SCADA directly to internet
• Confusing DMZ with power backup
• Assuming DMZ is a software tool

3. Given this firewall rule snippet for a SCADA DMZ:

ALLOW TCP FROM 192.168.1.0/24 TO 10.0.0.5 PORT 502
DENY ALL FROM ANY TO 10.0.0.5 PORT 502

What will happen if a device with IP 192.168.1.10 tries to connect to 10.0.0.5 on port 502?

medium

A. Connection will be logged but not blocked

B. Connection will be denied

C. Connection will be allowed only if using UDP

D. Connection will be allowed

Solution

1. Step 1: Analyze the first rule

   The first rule allows TCP traffic from 192.168.1.0/24 subnet to 10.0.0.5 on port 502.

2. Step 2: Check the second rule

   The second rule denies all other traffic to 10.0.0.5 on port 502.

3. Step 3: Determine rule precedence

   Firewall rules are processed top-down; the first matching rule applies.

4. Final Answer:

   Connection will be allowed -> Option D

5. Quick Check:

   Allow rule matches first = A [OK]

Hint: First matching rule applies in firewall rules [OK]

Common Mistakes:

• Ignoring rule order and choosing deny
• Confusing TCP with UDP protocols
• Assuming all traffic is denied by default

4. A SCADA firewall configuration has this rule:

DENY TCP FROM ANY TO 10.0.0.10 PORT 80

But users report they can still access the web interface on 10.0.0.10. What is the most likely cause?

medium

A. The rule is placed after an ALLOW rule that permits the traffic

B. The firewall does not support TCP filtering

C. Port 80 is not the correct port for web access

D. The IP address 10.0.0.10 is incorrect

Solution

1. Step 1: Understand firewall rule order

   Firewall rules are processed in order; the first matching rule applies.

2. Step 2: Identify rule placement issue

   If a prior ALLOW rule permits traffic to 10.0.0.10 on port 80, the DENY rule after it will not block it.

3. Final Answer:

   The rule is placed after an ALLOW rule that permits the traffic -> Option A

4. Quick Check:

   Rule order affects blocking = A [OK]

Hint: Check rule order; first match wins [OK]

Common Mistakes:

• Assuming firewall ignores TCP filtering
• Thinking port 80 is wrong without checking
• Assuming IP address is incorrect without evidence

5. You want to design a SCADA network with a DMZ to isolate control devices from the corporate network. Which setup best improves security?

hard

A. Allow all traffic between corporate network and SCADA devices for easy access

B. Place SCADA devices in the DMZ and allow only specific traffic from the corporate network through a firewall

C. Place SCADA devices behind the corporate firewall without a DMZ

D. Connect SCADA devices directly to the corporate network with no firewall

Solution

1. Step 1: Understand DMZ role in SCADA

   A DMZ isolates SCADA devices from the corporate network to reduce attack risk.

2. Step 2: Apply firewall rules

   Allow only specific, necessary traffic from corporate network to SCADA devices through firewall.

3. Step 3: Evaluate options

   Place SCADA devices in the DMZ and allow only specific traffic from the corporate network through a firewall uses DMZ and firewall properly; others expose SCADA or allow unsafe access.

4. Final Answer:

   Place SCADA devices in the DMZ and allow only specific traffic from the corporate network through a firewall -> Option B

5. Quick Check:

   DMZ + filtered firewall access = D [OK]

Hint: Use DMZ plus filtered firewall rules for SCADA security [OK]

Common Mistakes:

• Connecting SCADA directly to corporate network
• Skipping DMZ and relying on firewall only
• Allowing all traffic for convenience