Targeted Reconnaissance of Cyber-Physical Transportation Infrastructure: Methodology, Visibility, and Defensive Priorities
Critical infrastructure includes systems in which digital control directly governs physical processes. Movable bridges, span controls, and associated port and coastal infrastructure represent clear examples of cyber-physical systems. In these environments, commands or state changes on the digital layer can produce immediate effects on marine traffic, road traffic, and public safety.
This article describes a low-volume, targeted reconnaissance approach applied to legacy platforms within these cyber-physical transportation environments. The work shows that narrow geographic and protocol-based queries can surface relevant exposures while maintaining useful signal quality. It also illustrates a practical reality: systems identified through this type of reconnaissance are also discoverable by others.
Exposure on industrial protocol ports does not equate to vulnerability. The presence of a device responding on a known industrial port indicates only that it is reachable. It does not mean the device accepts unauthenticated commands, that safety interlocks can be bypassed, or that physical actuation can be commanded without additional controls or conditions.
Methodology
The approach used narrow city-level geographic boundaries combined with specific industrial protocol ports. Queries focused on well-known ICS ports and were supplemented by product and platform indicators visible in service banners. Total query volume remained low, supporting the practicality of repeated execution for monitoring purposes.
This method produced higher relevance than broader state-level searches or global legacy operating system queries. City-level scoping combined with port filters consistently reduced noise from non-industrial sources while surfacing operationally relevant platforms.
Key Observations
Reconnaissance identified multiple legacy and older platform indicators within the scoped transportation and maritime corridors. In one location, more than 200 Siemens S7 devices were observed responding on port 102, with a notable concentration of devices within a single subnet block. Multiple clusters of Rockwell/Allen-Bradley devices were also identified on EtherNet/IP, including one corridor with 8–12 devices in close proximity. Older-generation compact PLCs remained persistently visible across multiple scans in at least one location.
Building automation platforms were additionally observed on BACnet ports in industrial corridor environments. These observations were derived from passive banner data.
Exposure remains distinct from vulnerability. The identification of legacy platforms through passive methods provides visibility into reachable systems but does not constitute an assessment of exploitability or operational risk.
Discoverability and Implications
Because these systems are indexed through standard reconnaissance techniques, they are also visible to threat actors. Concentrated deployments of legacy controllers on well-known ports represent higher-visibility targets. Devices that remain persistently reachable over time are easier to track and profile.
This visibility underscores the importance of understanding what is exposed in cyber-physical transportation environments rather than assuming such infrastructure remains obscure.
Defensive Recommendations
When these systems must be reachable, a layered defensive approach is warranted.
The primary and most effective controls are network segmentation combined with secure remote access methods, such as VPNs and jump hosts or secure access gateways. These measures significantly limit direct exposure.
Where direct exposure cannot be avoided, systems should be placed behind a properly configured firewall with restrictive inbound rules. Source IP allow-listing or similarly constrained access provides meaningful reduction in the accessible attack surface.
Translating the external port away from well-known defaults via firewall network address translation can serve as a supplementary measure to reduce automated scanning noise. This technique offers limited protection against targeted reconnaissance and should not be relied upon as a primary control.
An additional practical layer is lightweight, repeatable monitoring of legacy platform indicators using narrow queries focused on transportation and maritime corridors. This approach can provide ongoing visibility into changes in exposure at low cost.
The Awareness Gap
Many operators of cyber-physical transportation infrastructure, particularly local governments and smaller regional entities, manage systems with direct physical consequences but often operate with limited dedicated OT security resources. Broad exposure reports frequently do not translate into actionable information for these decentralized operators.
Improving awareness requires translating technical findings into practical, sector-specific guidance that accounts for resource constraints and operational realities.
Conclusion
Targeted reconnaissance of cyber-physical transportation infrastructure can surface legacy platforms with manageable query volume and useful signal quality. Because these systems are publicly discoverable, visibility into their exposure is a necessary step toward improved defense.
The most effective path forward combines network segmentation and secure remote access as primary controls, properly configured firewalls where exposure is unavoidable, port translation as a minor supplementary measure, and lightweight monitoring as an ongoing visibility layer. These measures, paired with improved outreach to the operators who manage these systems, provide a more practical foundation than reliance on obscurity alone.