SCADA Communication Protocols Explained: Choosing the Right Approach for Secure & Reliable Operations

Supervisory Control and Data Acquisition (SCADA) systems enable organizations to remotely monitor, control, and collect real-time data from industrial equipment and processes across distributed facilities. For a SCADA system to work effectively, all its parts (like RTUs, field sensors, and the central control interface), must stay in constant, secure communication. That’s only possible with secure, reliable communication protocols linking each and every component together.

By developing a highly secure communication protocol and an equally secure SCADA-integrated collaboration platform, your organization can more effectively safeguard its data and prevent breaches. 

Here’s how.

What Are SCADA Communication Protocols?

A SCADA system’s RTUs must follow communication protocols when transmitting information about the status of input and output equipment to remote sites. As a kind of “language,” communication protocols create a formal structure and rules for exchanging data between different components of the SCADA system. Without a communication protocol, data would be sent in raw formats, leading to vulnerabilities that can compromise compliance and general security.

While some SCADA systems rely on proprietary protocols, most modern systems utilize open-standard protocols for greater flexibility. 

Are SCADA Communication Protocols the Same as SCADA Communication Transmission Methods?

Sometimes confused, SCADA communication protocols are not the same as SCADA communication transmission methods. While protocols allow SCADA units to “talk” to each other by ensuring data is compatible across components, communication transmission methods facilitate those communications, essentially “carrying” the data between devices. 

The most common types of SCADA communication methods for transmission include serial links, Local Area Network to Wide Area Network (LAN to WAN), Transmission Control Protocol/Internet Protocol (TCP/IP), and Internet of Things (IoT).

3 Popular Open Standard SCADA Communication Protocols

While choosing a SCADA communication protocol, you must know some of the most popular options and how secure each is. Below, you can find a breakdown of the three most common communication protocols SCADA systems use for secure, compliant data exchange:

1. Modbus

Modbus is a communication protocol developed in 1979 by Modicon (now part of Schneider Electric) for use with programmable logic controllers (PLCs). It is widely used in industrial settings, including manufacturing, energy, and building automation systems. Modbus operates on both serial (RS-232, RS-485) and TCP/IP networks, making it flexible and accessible. 

Its simplicity and open-source nature have contributed to its continued popularity, allowing easy integration between various devices, such as sensors, actuators, and controllers in SCADA systems. This protocol’s low cost and ease of implementation have made it a go-to choice for industries prioritizing reliability and basic control functions.

Modbus Security Considerations

Originally, Modbus was not designed with security in mind, and on its own, it lacks built-in encryption, authentication, and integrity-checking features. This absence leaves Modbus networks vulnerable to several cyber threats, including data interception, unauthorized access, and manipulation. Without encryption, the data exchanged between devices can be easily monitored or tampered with by malicious actors. 

How to Mitigate Modbus Security Risks

it is highly recommended to deploy additional security layers, such as virtual private networks (VPNs) and firewalls, to protect data. Integrating Modbus with secure transport protocols like TLS or using newer variants like Modbus/TCP Security, which adds basic encryption and authentication, is essential for enhanced security. Regular firmware updates and proper network segmentation can further protect Modbus systems from unauthorized access and vulnerabilities.

2. DNP3

Distributed Network Protocol 3 (DNP3) was developed in the 1990s primarily for use in the electric utility industry and has since expanded to applications in other critical infrastructure sectors, including water and wastewater systems, oil and gas pipelines, and transportation networks. 

DNP3 enables reliable communication between SCADA master stations and remote terminal units (RTUs) or intelligent electronic devices (IEDs), offering robust features like time synchronization, event logging, and high reliability for real-time data collection. 

Its ability to handle large volumes of data efficiently and its built-in support for managing complex systems have made it a preferred choice for industries that require high-performance monitoring and control.

DNP3 Security Considerations

Although DNP3 is known for its reliability and performance, legacy versions don’t natively support encryption or advanced security features. While the protocol has introduced authentication mechanisms to verify device identities, it still relies on plaintext communication, leaving it vulnerable to cyberattacks, including man-in-the-middle and denial of service (DoS) attacks. 

How to Mitigate DNP3 Security Risks

To address these concerns, DNP3 implementations should employ secure transport layers like TLS/SSL, which provide encryption and ensure data confidentiality. Additionally, strong authentication methods, such as mutual TLS or certificate-based authentication, should be integrated to further protect the system from unauthorized access. Routine security audits and patching outdated systems are essential steps for mitigating the risks associated with DNP3-based SCADA systems.

3. MQTT

MQTT is a lightweight, publish-subscribe messaging protocol designed for real-time, low-bandwidth communication, making it ideal for applications where reliable communication is needed over unreliable networks. Its efficiency and scalability have made it particularly popular in Industrial IoT applications, including SCADA systems that monitor and control critical infrastructure. 

Manufacturing, agriculture, and energy industries use MQTT to collect data from sensors, control devices, and track assets. Its ability to function in constrained environments with limited bandwidth and support for bi-directional communication has contributed to its widespread adoption in systems requiring real-time monitoring.

MQTT Security Considerations

Despite its popularity, MQTT, in its basic form, does not provide inherent security features, which means it is susceptible to various security risks, such as unauthorized access and data tampering. While MQTT can support encryption if implemented over TLS/SSL, basic MQTT communication leaves data exposed to interception. 

How to Mitigate DNP3 Security Risks

Secure MQTT communication requires that organizations use TLS/SSL, provide encryption at the transport layer, authenticate clients and brokers using X.509 certificates, and implement Access Control Lists (ACLs) to restrict access to specific topics. Additionally, regular updates to MQTT brokers and clients are necessary to ensure the system remains resilient to emerging vulnerabilities.

SCADA Communication Protocol Security Best Practices

With most SCADA systems now networked or IoT-based, your SCADA network is likely vulnerable to cyber threats. To increase your system’s security, your communication protocols should:

• Utilize authentication mechanisms like multi-factor authentication, complex passwords, and role-based access controls
• Employ end-to-end encryption and communication protocols with encryption built in
• Implement network segmentation, firewalls, intrusion detection systems, micro-segmentation, anomaly detection tools, and security information and event management systems
• Restrict remote access with isolated remote sessions and time-limited credentials while only providing remote access to critical personnel
• Comply with relevant security standards in your industry (e.g., water and electrical utility companies’ SCADA communication protocols should meet IEC 62351-5 and the IEC 60870-5 series standards)

In addition to looking for SCADA communication protocols compatible with these best practices, it’s important to conduct regular protocol security assessments, vulnerability assessments, and employee cybersecurity training sessions. Your team should also develop an incident response plan to ensure everyone is on the same page if your SCADA communication network is compromised.

How Secure Communication Tools Support SCADA Data Integrity and Compliance

Though communication protocols safeguard data transmission between components of the SCADA system, they’re not designed to protect data transmission outside of the system itself—including all the communication a supervisory team must perform to ensure the safety and security of the system. As a potential component of a SCADA communication network, a communication platform with SCADA integrations can ensure data is transmitted to user devices and channels quickly and securely, with a wide array of SCADA-ready integrations.

When a communication platform integrates with industrial monitoring systems like SCADA, you can use alert-driven webhook and plugin integrations to stay fully informed about system events. If a system event has occurred or an alarm has been triggered, these communication tools can automatically send information about them to relevant desktop or mobile channels securely. The automatic and secure transmission of SCADA system data to channels and devices enables real-time communication between systems and teams.

The Benefit of Self-Deployed Communications Platforms

With most SCADA systems now networked or IoT-based, a self-deployable communication platform can also be beneficial. For example, if a cyber threat has infiltrated your network and devices, communications on that network will also be compromised and open to data breaches. However, employees will still need to communicate with one another while solving the breach and continuing to address any issues with the SCADA system. 

A self-deployed communication platform can operate independently outside your network, allowing for out-of-band incident response. As a result, employees can stay in contact while solving the breach and handling any potential issues with the SCADA system, even when their primary network is compromised. 

Mattermost: A SCADA-Integrated Communication Platform

Mattermost’s collaboration platform is designed to integrate with alert-driven SCADA plugins and meets a variety of compliance standards governing essential service industries, such as energy, utilities, and manufacturing. Our platform encrypts data at rest and in transit, includes authentication and access control features, and  complies with a variety of industry standards. 

Learn more about how Mattermost can support your SCADA communication network today.