ICS Security Assessment in Industrial Networks

Table of contents

• ICS Security Assessment what is it: definition and operational context
• Why it is crucial for industrial enterprises
• Phases of an ICS Security Assessment
• Assessment output and deliverables
• Recommended frequency and cyclicity
• Considerations on the required technical competence

The progressive convergence between OT (Operational Technology) and IT (Information Technology) environments has transformed industrial architectures into interconnected but also highly exposed ecosystems.

In this context, the ICS Security Assessment emerges as an essential component of any corporate strategy aimed at protecting industrial control systems, which today are frequently connected to the network and therefore potentially exposed to advanced attack vectors.

The aim of this article is to illustrate, with methodological rigor but also clarity, what an ICS Security Assessment is , what its purposes are, the operational phases, and why it must be considered a minimum requirement for operational resilience in increasingly sophisticated threat scenarios.

ICS Security Assessment what is it: definition and operational context

ICS Security Assessment, in its most comprehensive sense, is a structured cyber risk assessment process applied to industrial control systems (ICS) and OT infrastructures, with the aim of identifying systemic vulnerabilities, architectural anomalies, misconfigurations and potential attack surfaces.

In the industrial context, this involves the analysis of heterogeneous components, including:

• PLC (Programmable Logic Controllers)
• SCADA (Supervisory Control and Data Acquisition)
• DCS (Distributed Control Systems)
• RTU (Remote Terminal Units)
• HMI (Human Machine Interfaces)
• Industrial IoT and edge devices

Unlike traditional IT assessments, an ICS Security Assessment requires a deep understanding of the temporal dynamics, physical dependencies and functional implications that characterize industrial processes. Security cannot be separated from availability: each intervention must be compatible with uptime and functional safety requirements.

Why it is crucial for industrial enterprises

The growing exposure of ICS systems to IP networks and cloud services leads to an exponential increase in the attack surface.Statistics from recent years indicate that manufacturing sectors are one of the main targets of ransomware attacks, APTs and sabotage activities conducted by state and non-state threat actors.

An ICS Security Assessment allows you to:

• Quantify the risk associated with known and unknown vulnerabilities
• Verify compliance with international standards (e.g. IEC 62443, NIS2, NIST CSF)
• Identify lateral attack paths between IT and OT
• Detect potentially dangerous legacy configurations
• Define technical and organizational countermeasures consistent with the risk

• To protect integrity
  To protect the integrity of production processes and ensure operational continuity, each security solution must be integrated on a tailor-made basis, through an assessment that takes into account the peculiarities of the physical-cybernetic systems involved.

Phases of an ICS Security Assessment

A comprehensive assessment requires a holistic, multidisciplinary and risk-oriented approach. The main operational phases include:

1. OT asset identification and profiling

The first phase consists of a detailed mapping of the devices and systems present in the ICS/OT network. This inventory can be conducted by:

• Passive asset discovery (e.g. Nozomi Guardian, Claroty)
• Network traffic analysis
• Technical documentation and interviews with OT managers

The lack of an updated asset inventory is in itself a risk indicator. Profiling should include attributes such as firmware, configurations, open ports and active connections.

2. Security posture analysis

This phase involves the identification of known exploitable vulnerabilities , using updated databases such as NVD, ICS-CERT Advisories, MITRE ATT&CK for ICS. The analysis can be conducted through:

• Non-intrusive vulnerability scanning (e.g. Nessus, OpenVAS in passive mode)
• Security configuration auditing
• Patch Policy Validation

Example
An unpatched Siemens S7-1200 PLC may be vulnerable to CVE-2020-15782, allowing an attacker to alter control logic without authentication.

3. Risk assessment and threat modeling

In this phase the risk is modelled according to methodologies such as:

• Bowtie model
• Attack tree analysis
• STRIDE for Threat Modeling

Each vulnerability is contextualized with respect to the network topology, the role of the asset, the Correlation example:

Vulnerability on HMI → Non-segmented OT network → Lateral access to PLC → Setpoint manipulation → Production interruption

4. Segmentation and communication analysis

The “zone and conduits” principle provided by IEC 62443 must be strictly applied. The assessment verifies:

• Isolating OT VLANs from IT Networks
• Existence and configuration of DMZs
• ICS Data Flow Logging
• Remote access (VPN, RDP, direct access over the Internet)

Analysis with tools such as Wireshark, Zeek or flow analytics helps determine if a control system is exposed to unauthorized access.

5. Evaluation of existing countermeasures

The team verifies whether the implemented security solutions are effective and correctly configured. This includes:

• Intrusion Detection Systems (Industrial IDS/IPS)
• Role-based access controls (RBAC)
• Log Management & SIEM
• Air-gapped backup and disaster recovery

The assessment may also include misconfiguration resistance tests, such as simulated shutdown of an HMI to analyze SCADA system reactions.

Assessment output and deliverables

At the conclusion of the process, the report should include:

• Updated topological map of the ICS system
• Documented and categorized vulnerabilities for CVSS
• Regulatory compliance assessment
• Risk analysis with impact and probability
• Roadmap for system hardening
• Prioritization of remediation activities

A well-written report can be the basis for obtaining budgets, defining intervention SLAs, and planning cyber hygiene in the long term.

Recommended frequency and cyclicity

An ICS Security Assessment must be performed at least:

• Annually (in the absence of critical events)
• Following the integration of new OT assets
• After incidents or detections from IDS/SIEM
• In correspondence with regulatory audits or certifications

More mature companies adopt a continuous approach (cyber security lifecycle) and integrate the asset discovery and anomaly detection function into the daily infrastructure management processes.

Considerations on the required technical competence

Unlike IT contexts, an ICS analysis requires a hybrid approach: knowledge of industrial automation, real-time networks, proprietary protocols (e.g. Modbus, Profinet, OPC-UA), but also a solid foundation in cyber security.

For this reason, it is recommended to select partners with vertical experience in the OT sector. Suppliers must be able to combine:

• Industrial Uptime Sensitivity
• Ability to operate in safety-critical environments
• Use of non-invasive methodologies
• Certifications (e.g. GIAC-GICSP, IEC 62443 practitioner)

Questions and answers

1. Is the ICS Security Assessment invasive?
   No, if conducted with passive tools and OT-aware methodologies it does not compromise running processes.
2. What is the difference between an IT assessment and an ICS assessment?
   An IT assessment analyzes generic IT assets, an ICS assessment focuses on industrial automation and control environments, requiring specialized approaches.
3. Is it required by law?
   In regulated sectors yes (energy, transport, water), otherwise it is strongly recommended according to NIS2 guidelines and international best practices.
4. Can I use open source software to do this internally?
   Some tools allow this, but specific technical expertise on OT environments and industrial protocol is required.
5. What risks are mitigated by assessment?
   Ransomware, APT attacks, internal sabotage, intellectual property theft, process manipulation.
6. Are there any reference frameworks?
   Yes: IEC 62443, NIST CSF, ISO 27019, Purdue Model.
7. Is it enough to do the assessment only once?
   No. The ICS landscape is evolving. New vulnerabilities and architectural changes require periodic reassessments.
8. How long does a full assessment take?
   2 to 8 weeks, depending on the complexity of the system and the availability of information.
9. Is it possible to integrate the assessment with SIEM/SOC tools?
   Yes, the output can feed into monitoring and incident response processes.
10. What is the ROI of ICS Security Assessment?
    Very high: the costs of the analysis are far lower than the potential damage resulting from an industrial cyber attack.