How to ensure OT secure remote access and prevent attacks

What is OT remote access?

OT remote access enables off-site users and locations to connect to industrial control systems (ICSes), SCADA systems and similar environments. This lets organizations maintain, troubleshoot and monitor OT systems, and gives industrial operators the tools they need to maintain and control their systems efficiently, improve system reliability and lower system response times.

OT secure remote access challenges

Despite the benefits, OT remote access opens the door to many security challenges.

Two major IT secure remote access challenges are uptime and legacy technology. First, OT systems support the production processes that deliver power, energy, water, waste and other critical services. They must operate 24/7 year-round, with little to no downtime. Taking them offline to apply patches is simply not an option, in many situations.

Second, many OT systems -- and the ICS and SCADA systems they connect to -- rely on legacy technology that either cannot support patches and other updates or is so old that it no longer has vendor support.

Additional OT security challenges include the following:

• Lack of proper network segmentation. When there is minimal separation between IT and OT networks, the attack surface increases. Without adequate network segmentation, the network is vulnerable to having its defenses compromised.
• Ineffective authentication capabilities. Many OT ecosystems are directly integrated with legacy technology that often has limited authentication controls. Additionally, most OT systems commonly use weak passwords or shared credentials. This makes it harder to implement stronger authentication security controls, such as two-factor authentication (2FA) and MFA.
• Third-party and supply chain risks. Working with external vendors is now a necessity for most businesses. But security gaps can occur when third parties can remotely access an OT network. Supply chain attacks can occur if vendor access policies are mismanaged or ineffectively monitored.
• Insufficient logging and monitoring. Using ineffectively secured programs, such as Remote Desktop Protocol, VPNs or other cloud-based tools, could introduce more vulnerabilities. This opens the door to phishing attacks, infostealers and other forms of credential theft. Limited security event logging also makes it tough for incident response teams to counter security incidents.

When OT systems are compromised, the damage reverberates quickly. Case in point: the Colonial Pipeline attack in 2021. In this breach, threat actors were able to remotely deploy ransomware that crippled fuel supply chains on the East Coast of the U.S. The pipeline had to be taken offline and required fuel resources to be diverted from other pipelines while Colonial remediated the ransomware from critical systems.

How to secure OT remote access

OT remote access systems require a mix of security controls and measures to proactively protect them from cyberthreats. Following are several key strategies that can yield positive results and help organizations better secure OT remote access systems:

• Adopt a zero-trust security approach to always verify, then trust, before authenticating.
• Properly segment IT and OT networks to isolate them from one another.
• Monitor and conduct ongoing audits of OT environments to ensure all remote access is authorized.
• Implement strong authentication protocols that require either 2FA, MFA or role-based access controls to ensure OT secure remote access systems and prevent unauthorized access.
• Disable insecure remote access communication protocols, such as Telnet, and use secure alternatives, for example, SSH, HTTPS and Secure File Transport Protocol.
• Use endpoint detection and response to help identify and mitigate threats from compromised remote devices.
• Apply patch management policies to ensure secure OT remote access tools and OT systems are up to date.
• Develop and test a comprehensive incident response plan that details organizational security gaps and provides guidance about how to manage breaches more proactively.
• Require third-party vendors to adhere to more cybersecurity procedures and deploy time-restricted or approval-based access for all vendors.
• Educate employees with simple and effective security awareness training that empowers them to act if they see something suspicious.

Amanda Scheldt is a security content writer and former security research practitioner.