Is Your Legacy System Leaving You Open to Cyber Threats? Protect Now

First, take stock of your legacy components and map data flows across your internet perimeter. Build a plan that targets the riskiest parts and aims for measurable wins in the next months. By organising assets, you're able to prioritise patches, access controls, and monitoring where it matters most, ensuring data safety during migration.

Relatively small, slow, targeted changes can dramatically reduce risk across years of accumulated exposure. In many shops, millions of lines of legacy programmes span multiple systems, so focusing on two or three critical interfaces can yield meaningful improvements within months and set you up for a longer, longer-term migration. This approach creates a longer path to full modernisation.

To sharpen protection, enforce right-sized controls: least-privilege access, multi-factor authenticationі short-lived credentials for administrative tasks. When you think about patching, schedule automations for the highest-risk parts and just-in-time updates, so you're not chasing fires in the dark.

Protect now with a concrete 90-day plan: map assets, isolate vulnerable parts, and implement continuous monitoring. We’ve seen organisations move from reactive to proactive in months, not years, by treating legacy as a programme with clear milestones, accountability, and measurable outcomes. By staying disciplined, you’re unlocking safer operations while keeping budgets in check and avoiding costly downtime, delivering better resilience.

Legacy System Cyber Risk: Practical Protection for Modern Connected Tech

Immediately segment production networks to isolate legacy machines and start a 14-day patching sprint to close critical vulnerabilities.

Legacy systems create a dense attack surface in digital environments. Production processes rely on small, older machines that run 24/7 and are connected to links to newer IT assets. When these connections aren’t tightly controlled, vulnerability exposure rises and recovery becomes painful. In weeks of constant operation, the risk compounds and disrupts maintenance windows, forcing difficult trade-offs between production uptime and security.

Rowan notes that most incidents begin with a single compromised device; the cause often lies in weak access controls and unpatched software. To address this, run a focused area-by-area assessment, then expand to the full production footprint.

The assessment is based on Rowan's findings and real-world data about how links between machines drive exposure in production environments.

• Asset inventory and classification: document each machine, its OS version and patch status, and its network role; capture their internal links to controllers, historians, and ERP systems; tag by risk area and production impact.
• Segmentation and least privilege: place critical machines in isolated zones; disable direct inbound access; apply firewall rules that limit east-west movement within the plant network.
• Patch and vulnerability cadence: establish critical updates within 7 days, non-critical within 14–21 days; run weekly scans and verify fixes in a staging area before production deployment.
• Monitoring and detection: collect logs from OT and IT sides; set alerts for unusual process starts, credential use, or unexpected reboots; align monitoring with production hours to minimise false positives.
• Backups and resilience: run redundant backups, store copies offsite or air-gapped; test restore procedures monthly and document recovery RTOs in the operations playbook.
• Governance and training: assign internal owners per area; formalise change controls; run drills to realise response times and ensure teams can collaborate across interfaces.

Practical protection comes from a staged mix of controls, not a single fix. By focusing on the right machines, reducing complexity, and building repeatable processes, you shorten the pain window and protect ongoing production from a cyber threat that targets ageing equipment. Start small, expand as needed, and measure progress in weeks with clear links between actions and risk reduction.

Identify Legacy Components That Pose Immediate Security Risks

Audit your asset catalogue today to locate legacy components that pose immediate security risks. Map each item by name, version, EOL status, and vendor support to establish a risk score for your current operations. Identify which systems still rely on outdated authentication methods or expose unencrypted data paths. Leave the most exposed items on a quick remediation plan and mark those that require migration.

Establish a dynamic inventory with fields for supplier, patch cadence, and integration points. Tie each item to potential exposure in the global network and to potential impact on critical workflows. Keep the data lean and update every few weeks to reflect new findings, so your team can move decisively rather than chase shadows.

Prioritise remediation by focusing on authentication bridges, legacy web apps, and API connections that still permit weak credentials or token reuse. If upgrade timelines extend, move those components into a segmented zone and enforce MFA, strict access controls, and continuous monitoring. This reduces the attack surface while you plan longer term steps.

Discontinue or retire components where possible. If retirement isn't feasible, limit external exposure, remove public endpoints and require signed updates from vendors. These moves can stop criminals from abusing outdated tech and keep operations stable as you modernise.

In Deloitte's current case notes, a global source confirms that legacy components were responsible for a sizeable share of breaches tied to outdated tech. Addressing these elements in weeks rather than months reduces risk and keeps you competitive as you move fast with modernisation.

Include a practical playbook for teams: inventory, set thresholds, require MFA, push updates from vendors, and plan phased decommissioning. This is an opportunity to reduce risk now whilst keeping scalable operations across the global footprint.

Construct a scalable modernisation roadmap with clear milestones and measurable outcomes. Focus on reducing reliance on older tech, migrating to modern containers or microservices, and consolidating tools within a unified security model. Align with current regulatory expectations and your competitive strategy to stay aligned with peers.

Audit Interfaces: Unsecured APIs, Remote Access, and Console Ports

Audit all interfaces now and shut down any unsecured APIs, remote access, and unused console ports that you don't need. This first and foremost step reduces thousands of risks that threaten operations and frees people up to focus on higher-priority work. This best practice also gives you more visibility into the risks.

These interfaces are composed of several components that connect to your core systems. Create a repeatable process to inventory existing interfaces and equipment that present exposure. These records should include owners, current status, and encryption support, so you can see who or what is allowed to connect and how. Keep notes about changes for audit and compliance. This set of steps makes a daunting task manageable.

Limit access through least-privilege controls: require MFA for remote access, disable default credentials, and integrate API gateways with your identity provider. Deny by default, and enforce encryption for data in transit and at rest. Present a clear catalogue of these connections to security governance so that management can approve changes quickly and consistently. Implement controls that actively support securing these connections. These ways to restrict access reduce surface area. This offer will provide a visible ROI by reducing unauthorised access harms.

These measures address the majority of breaches that start with exposed interfaces. Back up data and ensure encrypted backups, and set policy to decommission unused ports and endpoints promptly. Even in complex environments, monitoring and response routines stay effective. Establish continuous monitoring of access events, alert on anomalous patterns, and document responses in your operations playbooks. These steps help you move from reaction to a proactive security posture whilst reducing the chance of a failure that could disrupt thousands of transactions.

Prioritise Patch and Upgrade Paths with a Risk-Based Timeline

Implement a risk-based timeline for patch and upgrade paths now: patch high-risk devices within 14 days, upgrade critical systems within 30 days, and address medium- and low-risk assets within 60 to 90 days, depending on operations. Use a simple risk score that blends exposure, likelihood, and business impact to drive priorities, reducing complexity and enabling precise resource use. Align this with solutions and advisories from vendors so teams act on what matters there and you can manage risk effectively.

Create a rolling cadence by using continuous monitoring and global advisories to refine timelines, which helps teams stay aligned. If an advisory likely signals exploitation, accelerate the patch path and stop non-essential changes to free resources for remediation, while you scale even as you grow. Work with providers and peers, including peasley, to expand capabilities and keep devices protected while maintaining a predictable, auditable process.

Operationalise by mapping owners to each risk tier, tying actions to a shared process, and tracking progress in a centralised backlog within your programme. For small teams, focus on needed assets and critical segments; for global deployments, synchronise patches across regions to prevent outages. Consider the required capabilities and automate repetitive steps so you stay within realistic timelines. There is no room to leave gaps in protection, so set hold and stop thresholds when testing reveals compatibility issues.

Implement Network Segmentation and Least-Privilege Access

Start with a concrete action: map all critical assets and place them into a segmented network with clear boundaries between zones. Use a default-deny posture and implement strict access controls for each segment. This brings clarity to who can reach what, and it reduces the blast radius if a breach occurs, addressing risk in the current infrastructure without waiting for a full rewrite. Inevitable threats exist, so containment matters.

Adopt a least-privilege model: grant users and services only the minimum rights needed to perform tasks, and enforce this at the network edge and within each segment. Use RBAC or ABAC, tied to department role and project context. Implement time-bound credentials and automatic revocation to prevent drift. Sometimes you tailor policies to specific segments to balance security with usability. Apply specialised templates for sensitive segments to codify controls. This approach minimises exposure for hacked credentials and is especially effective against lateral movement.

Implement microsegmentation for workloads; place front-end and database tiers in separate segments; apply firewall policies that vary by service and data sensitivity. This approach extends policy enforcement to east-west traffic with specialised monitoring. This increases visibility nearly in real time and reduces risk while preserving performance.

Establish a governance cadence: quarterly reviews of access, continuous monitoring, and automated alerting when a segment is accessed outside of policy. In a hacking incident, segmentation reduces impact, and the current approach limits spread. This reduces long-term risk. Post-incident analysis should address gaps in the network and adjust rules; this ongoing effort fosters innovation and keeps your protection current.

Address long-term maintenance by keeping an up-to-date map of the network, covering specialised devices and endpoints, and running regular penetration tests to validate segmentation. Track metrics such as time to revoke access, number of segments, and reduction in lateral movement risk. When you present results to the department, emphasise higher protection and competitive advantage gained by tighter security. Allocate long-term resources for this effort.

Develop an Actionable Modernisation Roadmap for Compliance and Resilience

Start with a 90-day sprint that targets high-risk components and network-edge assets. This plan includes a concrete replacement plan for outdated systems and upgrades to reduce exposure from compromised endpoints. It keeps the focus on high impact risks.

Lead with a leader-driven inventory and assessments to identify which devices are compromised, where data flows from critical systems to the network, and which issues create the biggest risks. Map controls to regulatory requirements and document remediation gaps. Include companies in scope to address multi-vendor supply risk.

Craft a phased modernisation roadmap based on risk, not trendiness. Phase 1 focuses on fast upgrades and replacement of unsupported software; Phase 2 strengthens network segmentation and access controls; Phase 3 builds resilience with backup, incident response playbooks, and recovery plans aligned with realistic metrics. The daunting task becomes manageable when you convert it into small change steps, and avoid a slow rollout that stalls gains.

Establish a tight change programme with a clear funding model. Present a milestones table tied to upgrades, replacements, and technology refresh cycles. Assign accountability to a leader, with cross-functional programmes across IT, security, compliance, and risk management. Based on risk assessments, set budgets for replacements, monitoring, and training; expect measurable reductions in attacks and threats.

Implement continuous monitoring and assessments to keep the roadmap current. Use automated assessments to verify controls and ensure they remain effective, track which controls remain in place, and issue alerts when threats exceed tolerance. Align with vendor roadmaps for replacements and upgrades to maintain support over years, not waiting for a crisis. Pull in time-to-value metrics to demonstrate progress.

Adopt a technology-forward stance that brings time to respond and reduces the mean time to detect. Use other programmes as benchmarks and learn from real-world threats. Ensure documentation is based on current data and include a regular review cycle to prevent backsliding. The result is a resilient, compliant posture that will remain robust against attacks.