Why Penetration Testing Matters for Passenger Transit

Modern passenger transit systems rely heavily on digital infrastructure to deliver safe, efficient and reliable service. From fare collection and passenger Wi-Fi to train control and signaling systems, technology is now embedded in nearly every operational function. As these systems become more interconnected, the risk of a cyberattack capable of disrupting operations increases. The impact of such an attack can be devastating, halting service and compromising sensitive data.  

In recent years, ransomware and network intrusions have targeted multiple North American transit agencies, often exploiting weak remote-access controls, outdated software or vulnerable third-party systems. Federal agencies have responded with new directives and guidance to strengthen cybersecurity across the transportation sector. The Transportation Security Administration (TSA) now mandates cybersecurity risk assessments and incident reporting for high-risk operators, while the Cybersecurity and Infrastructure Security Agency (CISA) emphasizes proactive testing as a cornerstone of modern cyber defense.  

Penetrating testing, sometimes referred to as ethical hacking, provides a structured, authorized means of identifying vulnerabilities before malicious actors can exploit them. By simulating real-world attacks in a controlled manner, transit agencies can uncover exploitable weaknesses, validate defenses and make informed decisions about cybersecurity investments and risk management. 

CISA’s 2023 Cybersecurity Best Practices for Transportation Systems and the TSA’s Security Directive Surface 2021-02D both highlight continuous assessment and testing as essential elements of a comprehensive cybersecurity program. 

The transit cyber threat landscape 

Transit agencies operate within one of the most complex and visible cybersecurity environments in the public sector. Their systems often blend traditional information technology (IT), operational technology (OT) and Internet of Things (IoT) devices, creating a vast and interconnected attack surface. Adversaries range from nation-state actors seeking disruption or intelligence to organized ransomware groups pursuing financial gain. Hacktivists may deface passenger information systems while insider threats persist due to distributed workforces and contractor dependencies.  

Common attack methods include phishing campaigns that steal credentials, exploitation of insecure remote-access tools used for maintenance or vendor support and infiltration through vulnerable supply chains. Increasingly, adversaries are also taking advantage of poorly secured IoT systems, such as passenger counters, security cameras and connected fare devices. Once inside a network, they may move laterally between administrative IT and mission-critical OT systems such as signaling or control centers.  

Frameworks like MITRE ATT&CK for Industrial Control Systems (ICS) may help agencies understand these threats in detail, mapping adversary tactics such as gaining access through exposed services, moving laterally via trusted connections and disrupting operations by tampering with data or disabling systems. CISA’s ICS advisories further highlight the evolving nature of these threats, providing actionable information for transit operators seeking to mitigate them.  

What penetration testing is (and isn’t) 

Penetration testing is the authorized simulation of cyberattacks to identify vulnerabilities in an organization’s systems, networks or applications. Unlike automated vulnerability scans that detect known weaknesses, penetration testing involves expert analysis and controlled exploitation to determine whether vulnerabilities can actually be used to compromise systems. The goal is not to cause harm, but to provide evidence-based insights into real-world risk. 

It is important to distinguish penetration testing from other forms of security assessment. While vulnerability assessments simply report potential weaknesses and compliance audits ensure adherence to policies or regulations, a penetration test actively evaluates whether those controls are effective under realistic attack conditions. Similarly, a red team exercise differs from penetration testing in that it focuses on testing detection and response capabilities without prior notice provided to network defenders.  

In the transit environment, testing typically encompasses enterprise IT systems such as email servers and fare collection platforms, OT networks like signaling and supervisory control and data acquisition and connected IoT devices, including surveillance cameras and passenger information systems. Because these environments directly support public safety and service continuity, all testing must be carefully planned, authorized and executed to avoid operational disruption. The principles and processes for such testing are well documented in the National Institute of Standards and Technology’s (NIST) Special Publication 800-115: Technical Guide to Information Security Testing and Assessment.  

Planning and scoping a penetration test 

The success of a penetration test depends on thorough planning and clear definition of scope. A well-scoped test identifies which systems will be examined, which methods are permitted and how safety and operational continuity will be maintained. For transit agencies, this process begins with developing a comprehensive inventory of all hardware, software and communications systems utilized by the agency or its third parties. These assets are categorized by risk level and operational criticality through a business impact analysis (BIA), a key step in cybersecurity risk management.  

Once systems are identified, leadership and cybersecurity teams must define the objectives of the test. Some agencies may choose to focus on validating network segmentation between IT and OT while others emphasize assessing the security of remote access pathways or cloud-hosted passenger data. All testing must be formally authorized by executive leadership, and the rules of engagement must clearly outline what testers can and cannot do.

For example, rules of engagement often exclude destructive test methods or denial-of-service because of the potential damage to agency systems. Coordination with operations and safety departments ensures that testing occurs during appropriate maintenance windows or non-peak hours to prevent service disruption. 

Data protection and privacy are also critical considerations during the scoping phase. Transit systems handle sensitive operational data and sometimes personally identifiable information from fare transactions, so secure data handling procedures must be enforced throughout the engagement. Many agencies begin their security assessment process by leveraging the federal CISA Cyber Hygiene Services program, which provides free vulnerability scanning for public-facing systems. The result of these scans can then be used to inform and prioritize targeted penetration testing engagements.  

Testing and techniques 

A typical penetration test follows a structured methodology that progresses through several phases. During reconnaissance, testers gather open-source intelligence and map the agency’s digital footprint, identifying domains, IP ranges and exposed services. In transit environments, this may include locating contractor virtual private network portals, maintenance interfaces or legacy web applications.  

The next phase, vulnerability detection, involves both automated scanning and manual verification to pinpoint weaknesses such as outdated software, misconfigured firewalls or weak authentication mechanisms. Once vulnerabilities are confirmed, the exploitation phase begins. Here, testers simulate an attacker’s actions to determine whether the weakness can actually be exploited or if alternative defensive measures prevent exploitation.  

Following exploitation, the post-exploitation phase assesses the potential impact of a compromise. In a transit context, this means testing whether an attacker could laterally move from an IT network into operational systems like signaling control networks. Each step is conducted carefully under strict operational safety guidelines.  

When testing concludes, the agency receives a comprehensive report that includes detailed technical findings, severity ratings and remediation recommendations. Executive summaries translate technical outcomes into language to be used by decision-making leadership. The MITRE ATT&CK for Enterprise framework and the FTA Cybersecurity Toolkit for Transit Agencies offer additional guidance for aligning testing outcomes with established practices.  

Case study: Targeted penetration testing engagement 

A regional transit agency engaged a certified penetration testing team to evaluate its fare-collection system and supporting infrastructure. The assessment included both external and internal testing under defined constraints. 

Externally, testers performed network reconnaissance and web application analysis against the agency’s online fare payment portal. Using industry standard tools such as NMAP and BurpSuite, they identified a cross-site scripting vulnerability. Controlled exploitation demonstrated limited access to a staging environment, confirming that proper network segmentation prevented lateral movement. Credential testing also revealed default administrative passwords in a legacy management interface. 

Internally, testers reviewed domain configurations, endpoint security and credential management. They discovered unpatched systems susceptible to privilege escalation and lateral movement through SMB vulnerabilities. Weak password reuse across multiple service accounts posed additional escalation risks.  

Recommendations included enforcing multifactor authentication for privileged users, implementing endpoint detection and response visibility across OT gateways and tightening network segmentation rules. The engagement produced a clear roadmap of prioritized mitigations that could be implemented without operational disruption, demonstrating how targeted penetration testing can reveal critical security gaps.  

Using results for risk management 

Penetration testing delivers lasting value only when results are integrated into an agency’s broader risk management and safety programs. Each identified vulnerability should be documented and prioritized using the Common Vulnerability Scoring System, which accounts for both technical severity and operational impact.  

Test results should align with the NIST Cybersecurity Framework, helping agencies manage cybersecurity risks across its five core functions: identify, protect, detect, respond and recover. Integrating outcomes into these functions enables agencies to track progress, address deficiencies and strengthen their cybersecurity posture.  

Many agencies also align penetration testing with their safety management system processes to ensure that cybersecurity risks are treated with the same rigor as physical safety hazards. Testing results can be used to justify investments in security technology, inform workforce training and guide policy development. Once mitigation measures are in place, retesting confirms that vulnerabilities have been effectively resolved.  

Building a sustainable testing program 

Penetration testing should be treated as an ongoing process rather than a one-time compliance activity. A sustainable testing program allows agencies to continuously monitor progress and adapt to evolving threats. It’s recommended that agencies conduct comprehensive testing at least once a year and more frequently following major technology upgrades or prior to an anticipated change to the threat landscape.  

Security validation should also be incorporated into project lifecycles. Before deploying new technologies, agencies should include security testing as part of pre-deployment acceptance. This helps agencies understand the cyber risk of a system before it enters into the operational environment. Federal programs such as the TSA Cybersecurity Self-Assessment and CISA Cyber Hygiene initiatives offer valuable opportunities for agencies to benchmark their practices and identify areas for improvement.  

Finally, building a strong relationship with qualified penetration testing providers who understand the transit environment ensures that testing remains realistic, safe and aligned with regulatory expectations. Collaboration between internal defensive teams and external offensive teams fosters a culture of continuous improvement and operational resilience.  

From compliance to resilience 

As transit systems continue to digitize, cybersecurity resilience is inseparable from operational safety. Penetration testing offers an evidence-based approach to identifying vulnerabilities, validating defenses and meeting federal requirements, but its greatest value lies in empowering agencies to proactively manage cyber risk.  

By integrating penetrating testing into strategic planning and budgeting, agencies can evolve from a reactive cybersecurity posture to a proactive one prepared to withstand modern threats. Leveraging frameworks from CISA, TSA, NIST and MITRE, transit operators can ensure that the systems moving millions of passengers each day remain efficient, safe and secure.