Network segmentation (IT/OT separation) in SCADA systems - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a VLAN for the OT network segment.

SCADA systems

vlan [1] {
  name "OT_Network"
}

Drag options to blanks, or click blank then click option'

A10

B30

C20

D40

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing VLAN ID 10 which is often used for IT networks.

The OT network VLAN is commonly assigned VLAN ID 20 to separate it from IT networks.

2fill in blank

medium

Complete the firewall rule to allow only Modbus TCP traffic from IT to OT segment.

SCADA systems

firewall rule allow_modbus {
  source vlan IT
  destination vlan OT
  protocol [1]
  port 502
}

Drag options to blanks, or click blank then click option'

Audp

Bicmp

Chttp

Dtcp

Attempts:

3 left

💡 Hint

Common Mistakes

Using UDP or ICMP which are not correct for Modbus TCP.

Modbus TCP uses TCP protocol on port 502, so the protocol must be set to tcp.

3fill in blank

hard

Fix the error in the ACL to block all traffic except SSH from IT to OT.

SCADA systems

acl it_to_ot {
  permit [1] any any eq 22
  deny ip any any
}

Drag options to blanks, or click blank then click option'

Atcp

Budp

Cicmp

Dip

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'ip' or 'udp' which do not match SSH protocol.

SSH uses TCP protocol on port 22, so the permit rule must specify tcp.

4fill in blank

hard

Fill both blanks to create a subnet for the OT network and set the correct mask.

SCADA systems

subnet [1] [2] {
  description "OT subnet"
}

Drag options to blanks, or click blank then click option'

A192.168.50.0

B255.255.255.0

C255.255.0.0

D10.0.0.0

Attempts:

3 left

💡 Hint

Common Mistakes

Using 10.0.0.0 which is usually for IT or other segments.

The OT subnet uses 192.168.50.0 with a mask of 255.255.255.0 for a typical /24 network.

5fill in blank

hard

Fill all three blanks to define a firewall rule allowing HTTPS from IT to OT with logging enabled.

SCADA systems

firewall rule allow_https {
  source vlan [1]
  destination vlan [2]
  protocol [3]
  port 443
  log enable
}

Drag options to blanks, or click blank then click option'

AIT

BOT

Ctcp

Dudp

Attempts:

3 left

💡 Hint

Common Mistakes

Using UDP protocol or reversing source and destination VLANs.

HTTPS traffic is TCP on port 443 from IT VLAN to OT VLAN, so source is IT, destination OT, protocol tcp.

Practice

1. What is the main purpose of network segmentation between IT and OT systems in SCADA environments?

easy

A. To improve security by separating critical industrial systems from general IT networks

B. To increase the speed of data transfer between devices

C. To reduce the number of devices needed in the network

D. To allow all devices to communicate freely without restrictions

Solution

1. Step 1: Understand the role of network segmentation

   Network segmentation divides a network into parts to isolate sensitive systems from less secure ones.

2. Step 2: Apply this to IT and OT systems

   Separating IT (office systems) from OT (industrial control) protects critical SCADA systems from cyber threats.

3. Final Answer:

   To improve security by separating critical industrial systems from general IT networks -> Option A

4. Quick Check:

   Network segmentation = Security improvement [OK]

Hint: Segmentation means separation for security, not speed or device count [OK]

Common Mistakes:

• Thinking segmentation speeds up network
• Believing segmentation reduces devices
• Assuming segmentation allows free communication

2. Which of the following VLAN configurations correctly separates IT and OT traffic?

easy

A. VLAN 20 for IT devices, VLAN 10 for OT devices, but no traffic control

B. VLAN 10 for both IT and OT devices without any ACLs

C. VLAN 10 for IT devices, VLAN 20 for OT devices, with ACLs controlling traffic between them

D. No VLANs, all devices on the same network segment

Solution

1. Step 1: Identify VLAN usage for separation

   Using separate VLANs for IT and OT devices isolates their traffic logically.

2. Step 2: Check for access control lists (ACLs)

   ACLs control and restrict traffic between VLANs, enhancing security.

3. Final Answer:

   VLAN 10 for IT devices, VLAN 20 for OT devices, with ACLs controlling traffic between them -> Option C

4. Quick Check:

   Separate VLANs + ACLs = Proper segmentation [OK]

Hint: Separate VLANs plus ACLs control traffic properly [OK]

Common Mistakes:

• Using same VLAN for IT and OT
• Not applying ACLs between VLANs
• Ignoring VLANs and traffic control

3. Given this simplified network ACL rule:
permit ip 192.168.1.0 0.0.0.255 10.0.0.0 0.0.0.255
What does this rule allow?

medium

A. Allow all IP traffic from 192.168.1.x to 10.0.0.x

B. Block all traffic from 192.168.1.x to 10.0.0.x

C. Allow traffic only from 10.0.0.x to 192.168.1.x

D. Allow traffic from any IP to any IP

Solution

1. Step 1: Understand ACL syntax

   The rule permits IP traffic from source 192.168.1.0/24 to destination 10.0.0.0/24.

2. Step 2: Interpret the wildcard masks

   Wildcard 0.0.0.255 means any IP in the last octet, so 192.168.1.x to 10.0.0.x is allowed.

3. Final Answer:

   Allow all IP traffic from 192.168.1.x to 10.0.0.x -> Option A

4. Quick Check:

   permit ip source to destination = Allow traffic [OK]

Hint: permit ip source wildcard destination wildcard means allow that traffic [OK]

Common Mistakes:

• Confusing source and destination
• Misreading wildcard masks
• Assuming rule blocks traffic

4. You configured VLANs for IT and OT but OT devices cannot communicate with the SCADA server. What is the most likely cause?

medium

A. OT devices have incorrect IP addresses outside VLAN range

B. VLAN IDs for IT and OT are the same

C. SCADA server is powered off

D. Missing or incorrect ACL rules blocking OT to SCADA traffic

Solution

1. Step 1: Check VLAN separation

   If VLAN IDs are different, devices are separated logically, so VLAN ID conflict is unlikely.

2. Step 2: Review ACL rules

   ACLs often block traffic between VLANs; missing or wrong ACLs can prevent OT devices from reaching SCADA server.

3. Final Answer:

   Missing or incorrect ACL rules blocking OT to SCADA traffic -> Option D

4. Quick Check:

   ACL misconfiguration = communication failure [OK]

Hint: Check ACLs first when VLANs separate but no communication [OK]

Common Mistakes:

• Assuming VLAN IDs are same without checking
• Ignoring ACL impact on traffic
• Jumping to hardware power issues first

5. You want to allow only specific IT workstations to access OT SCADA devices. Which approach best achieves this while maintaining network segmentation?

hard

A. Place all IT and OT devices in the same VLAN to simplify access

B. Create a dedicated VLAN for those IT workstations and configure ACLs to allow only their IPs to OT VLAN

C. Disable all ACLs between IT and OT VLANs to allow free communication

D. Use a single firewall rule allowing all IT subnet to access OT subnet

Solution

1. Step 1: Understand segmentation with selective access

   Segmentation requires separate VLANs; selective access needs controlled rules.

2. Step 2: Apply VLAN and ACLs for fine control

   Creating a dedicated VLAN for allowed IT workstations and ACLs restricting access by IP ensures security and selective access.

3. Final Answer:

   Create a dedicated VLAN for those IT workstations and configure ACLs to allow only their IPs to OT VLAN -> Option B

4. Quick Check:

   Dedicated VLAN + ACLs = selective secure access [OK]

Hint: Use VLAN plus ACLs to limit access, not open networks [OK]

Common Mistakes:

• Mixing IT and OT in one VLAN
• Disabling ACLs completely
• Using broad firewall rules without IP filtering