The United Kingdom’s public sector is under increasing cyber pressure.
Government departments, healthcare systems, local councils, and public institutions now rely heavily on interconnected digital infrastructure. Much of that infrastructure was built years ago and still depends on ageing systems that are difficult to update, monitor, or secure properly.
At the same time, public sector software increasingly relies on open-source components. These dependencies help teams develop systems faster and reduce costs, but they also introduce software supply chain risk when vulnerabilities are not tracked or patched consistently.
Together, legacy infrastructure and unmanaged open-source dependencies are creating a difficult security environment. Attacks are becoming more disruptive, more expensive, and harder to contain.
Legacy Systems Remain Widespread Across the Public Sector
Legacy technology remains one of the biggest cyber security weaknesses inside UK public infrastructure.
The National Audit Office warned in 2025 that many government systems remain “high risk” due to age, unsupported software, and outdated architecture.

The UK government’s own Cyber Action Plan similarly acknowledged that some legacy systems cannot be defended effectively using modern security controls.
Many of these systems:
- Were built decades ago
- Cannot be patched easily
- Depend on outdated software stacks
- Lack compatibility with modern security tooling
- Require specialist maintenance knowledge
Replacing these systems is difficult. Large public sector upgrades are expensive, operationally risky, and often slowed by procurement complexity.
As a result, vulnerable systems frequently remain active long after safer alternatives are available.
Why Legacy Systems Increase Cyber Risk
Older systems are easier targets for attackers because they often lack basic modern protections.
Many do not support strong identity controls, modern encryption standards, or real-time threat monitoring. Some are no longer supported by vendors, meaning newly discovered vulnerabilities may never receive official patches.
Legacy systems also create wider operational risk because they are rarely isolated. Most are connected to newer applications, databases, cloud environments, or third-party services.
That means a vulnerability in one outdated system can become an entry point into a much larger network.
The National Audit Office has warned that ageing systems increase the likelihood of successful attacks and make incident recovery more difficult once breaches occur.
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Open-Source Software Adds Another Layer of Risk
Open-source software now powers most modern applications.
Public sector organisations use open-source frameworks, libraries, and packages across internal systems, citizen services, cloud applications, and third-party platforms.
The challenge is visibility.
Modern applications often contain hundreds or thousands of software dependencies, including transitive dependencies that developers may not even realise are present.
If organisations do not know which components exist inside their software, they cannot know which vulnerabilities affect them.
Research consistently shows that the majority of modern software contains open-source code. Many applications also contain known vulnerabilities that remain unresolved long after patches become available.
This is becoming a major concern for governments worldwide because vulnerable open-source components can spread risk across multiple systems at scale.
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The Log4j Problem Showed How Fast Risk Can Spread
The Log4j vulnerability remains one of the clearest examples of software supply chain risk.
Even years after the Log4Shell vulnerability was disclosed and patched, vulnerable versions continued appearing inside production systems worldwide.
Reports in 2025 showed that a significant percentage of Log4j downloads still contained vulnerable versions despite years of public awareness.

The issue was never simply the existence of the vulnerability itself. The larger problem was that many organisations did not know where Log4j existed inside their software stack.
This is the core software supply chain challenge facing public sector organisations today.
A single vulnerable dependency can quietly exist across government systems, suppliers, applications, and service providers without clear visibility.
Cyber Attacks Against Public Services Are Increasing
The cyber threat facing the UK public sector continues to intensify.
The National Cyber Security Centre reported a growing number of nationally significant cyber incidents in its latest annual review. State-backed threat actors, ransomware groups, and financially motivated attackers continue targeting public infrastructure because disruption creates immediate pressure.
Several recent incidents have shown how severe the consequences can become.
Healthcare Systems
The NHS has experienced repeated cyber incidents linked to outdated infrastructure and unpatched vulnerabilities.
These attacks disrupted services, delayed operations, and exposed sensitive patient information. Healthcare systems remain particularly vulnerable because they depend on large interconnected environments that are difficult to modernise quickly.
The British Library Attack
The cyber attack against the British Library became one of the UK’s clearest examples of how legacy technology can worsen the impact of a breach.
The incident caused major operational disruption and lengthy recovery efforts. Later analysis linked the severity of the attack partly to historic underinvestment in cyber resilience and ageing infrastructure.
Local Government Disruption
Local councils across the UK have also faced growing cyber pressure.
Attacks have disrupted housing systems, benefits administration, and citizen services. In some cases, organisations were forced to revert to manual processes while systems recovered.
For public services, cyber incidents quickly become operational problems rather than isolated IT failures.
Why This Is Becoming a National Resilience Issue
The combined effect of legacy systems and open-source vulnerabilities creates broader national risk.
These issues are interconnected.
A vulnerable open-source component inside a legacy environment can affect multiple public services simultaneously. Once attackers gain access, interconnected systems make lateral movement easier and containment harder.
The consequences can include:
- Service disruption
- Data breaches
- High remediation costs
- Operational downtime
- Delayed digital transformation
- Increased exposure to state-sponsored attacks
Public infrastructure now depends heavily on software resilience. When software supply chains become difficult to monitor, national resilience becomes harder to maintain.
What Needs to Change
The UK public sector does not need to stop using open-source software. That would be unrealistic and counterproductive.
The priority is visibility.
Public sector teams need to know which open-source components are inside their software, where vulnerable versions are being used, and which fixes are available. This needs to happen continuously, because new vulnerabilities emerge every day.
Security also needs to move closer to development. If vulnerable dependencies are only discovered late in CI/CD, or after deployment, remediation becomes slower and more expensive.
The strongest approach is to make dependency security part of the normal development workflow. Developers should be able to see vulnerable packages, understand the risk, and move to safer versions before code reaches production.
Conclusion
The UK public sector faces a layered cyber security problem.
Legacy systems create weak points. Unmanaged open-source dependencies add software supply chain risk. Together, they make public services more exposed to attacks that can disrupt operations, expose data, and damage national resilience.
Modernising public infrastructure will take time. But visibility over open-source risk can improve now.
Knowing what is inside public sector software is the first step toward protecting the services people rely on every day.














