The Dangers of Legacy Antivirus in Public Sector Organisations

"Antivirus is essentially a piece of software that you install on a client, be that a PC, a desktop or a server, and its prime focus is to protect against malware and ransomware," explains Kevin Prone, Head of Security Operations at FourNet. It's a simple premise that's protected organisations for decades by: 

1. Detect malicious code
2. Blocking it  
3. Keeping systems running safely

But in today's environment, where attacks are constantly evolving, that traditional model is showing its age. The UK public sector alone faces more than 2,000 cyber incidents each year, according to the National Cyber Security Centre (NCSC). Many of these threats now slip past traditional defences because they don't behave in the predictable ways older antivirus tools were designed to spot.

This means antivirus is still a critical line of defence, but no longer the only one. As attackers grow more sophisticated, defences must evolve from static tools into adaptive systems that understand intent, not just code.

"The first myth is that legacy AV is good enough," says Chris. "It protected me before, it'll protect me today. In reality, that's just not the case." Recent research backs this up: 82% of modern malware attacks aren't detected by traditional antivirus tools (CrowdStrike, 2024).

Other common myths persist:

• That skipping software updates is harmless
• That compliance equals resilience
• That upgrading is too costly or time-consuming to justify

Kevin adds "People think, 'I've got it [Antivirus], I've bought it, I'm fine.' But the threat isn't static, it's dynamic." Legacy AV gives the illusion of safety without real protection. The cost of an upgrade is nothing compared to the financial and reputational damage of an attack.

Legacy antivirus is defined not by its age, but by its limitations. "Legacy antivirus is essentially pattern-based," Kevin explains. "When you see red, certain things happen. When you see blue, certain things happen." These tools rely on recognising known patterns of malicious activity. The problem with that is that modern threats rarely follow a pattern.

Attackers now focus on how to evade detection. They use obfuscation, living-off-the-land tactics, and subtle behaviour shifts to slip through old defences unnoticed. As Steve Price, Enterprise Account Director at FourNet notes, "It's not as simple as downloading a malicious file anymore; it can be done piece by piece, quietly gathering information to drive a future attack."

That's when antivirus becomes legacy: when it's defending against yesterday's attacks instead of predicting tomorrow's.

Across the public sector (especially in Wales) legacy systems remain a daily challenge. "Budget is number one," says Chris Greenwood, Strategic Account Director at FourNet. "When you're choosing between an MRI scanner and antivirus software, the scanner often wins." Cyber projects compete for funds, even as threats escalate.

The second challenge is skills. Many Welsh councils and health boards struggle to recruit and retain cybersecurity specialists, particularly when the private sector across the M4 corridor offers higher pay.

Legacy infrastructure compounds the issue. Some systems can't be moved to the cloud, creating complex hybrid environments that are harder to secure. Add hybrid working, IoT devices and sprawling data estates, and the attack surface keeps widening.

This results in "Set and forget" antivirus tools that were installed years ago, updated sporadically and quickly become blind spots in otherwise modern networks.

Modern protection looks very different. "It's not just about pattern matching anymore," Kevin explains. "It's about understanding behavioural techniques, context, and intent."

Next-generation antivirus and Endpoint Detection and Response (EDR) tools now analyse live data to recognise trends, learn from threat intelligence feeds, and predict malicious behaviour before it happens. They combine pattern analysis, machine learning, and real-time context to stop threats that legacy tools can't see.

The evolution reflects a change in the attackers' playbook too. The fastest recorded breach time is now under three minutes, according to IBM X-Force. That speed demands technology that can detect, decide, and act automatically. The shift from reactive defence to proactive detection marks the biggest leap in cybersecurity since antivirus began.

AI has changed both sides of the fight. "Phishing emails are now written in perfect English," Kevin warns. "They reference things you've actually talked about. They're believable." AI gives attackers scale and sophistication, helping them craft messages that prey on urgency and trust.

But AI is also transforming defence. "We're using AI and machine learning in our correlation engines to make better, faster decisions," says Steve. In FourNet's Security Operations Centre (SOC), automation now handles much of the heavy lifting, linking data from multiple sources, spotting anomalies, and helping analysts focus on high-risk activity.

As Chris notes, "It's no longer just nation states. It can be a 16-year-old with access to a toolset online." The democratisation of cybercrime means every organisation, no matter its size, needs modern, AI-informed protection that can evolve as quickly as the attackers do.

For public sector organisations, frameworks like CAF (Cyber Assessment Framework) and Cyber Essentials Plus have become vital reference points. "They're not reinventing the wheel," Chris explains, "but they're raising the bar."

In Wales, the Cyber Security Action Plan and Digital Strategy for Wales have added practical funding and visibility to the issue. "You can't deliver better digital services without them being secure," Chris says.

Frameworks give structure, but they aren't the finish line. "Cybersecurity is a journey, not a destination," adds Kevin. "If you set and forget, your effectiveness falls back." The value of these frameworks lies in continuous improvement, testing, auditing, and adapting as threats evolve.

For organisations unsure where to start, Kevin's advice is simple: "Look at what you've got. Is it pattern-based, or is it able to make intelligent decisions?"

FourNet helps public sector teams assess that gap. Through quick, independent reviews, our experts identify whether you're in the legacy stage, a hybrid state, or a modern EDR environment ready for today's threats.

The group concluded that, "Every organisation has a business continuity plan, but not every one has a cyber continuity plan." The time to change that is now. With modern, context-aware protection and clear response planning, public sector teams across Wales and the UK can move from reactive defence to lasting resilience.