7 Principles for Hardening Mission-Critical Infrastructure Against Zero-Day Threats
Mission-critical infrastructure powers the lights, keeps the water flowing, and energizes the economy. But zero-day threats, or security flaws not yet known to software makers, make these critical systems extremely vulnerable. Real critical system protection is more than preventing attacks; it’s about resilience: keeping the operation going under testing conditions. This is an impossible task, even if the costs are public safety and billions of dollars lost; securing these systems requires a disciplined, layered defence.
Here are seven principles you can use to protect your most important assets from the unknown.
I. Continuous Visibility
You can’t defend what you can’t see. Continuous monitoring is the core of any Security Operations Centre. In 2023, the global median dwell time, or the amount of time that an attacker is present on a victim’s system before detection, decreased to 10 days. This is better, but it’s not going to help against a zero-day that can wreak havoc in minutes.
One way to prevent this is by deploying technology that maps all assets across the entire network. The result: No “shadow IT” or unmonitored devices leave a back door for attackers. If a box is attached to your critical infrastructure, then it needs to be “seen,” monitored, and accounted for.
II. Standardization
Complexity hides vulnerabilities. And by establishing a standard operating system, hardware, and configuration across your environment, you can establish a known-good baseline.
If every server and workstation is built to the same configuration standard, even the slightest deviation from that standard stands out like a sore thumb. This greatly simplifies the work of recognizing the subtle indicators that might accompany a zero-day attack: a rogue process coming to life or an unauthorized configuration change, for example.
III. Vulnerability Management
You might not be able to patch a zero-day flaw before it is released, but that doesn’t mean you should not have a strong patch management strategy. Attackers often “chain” zero-day exploits with older, known vulnerabilities to spread laterally through a network.
Attackers’ use of zero-days increased by more than 50 percent from 2023 to 2024, according to Mandiant. If you keep systems up-to-date and perform regular vulnerability assessments, you knock out the easy stepping stones that attackers use to elevate their privileges or get to critical controls.
IV. Prioritization
Not all assets are equal. Priority to systems is given, for security teams, according to the impact of failure. Unplanned downtime costs the average industrial company nearly $125,000 every hour, according to an ABB report.
Concentrate your toughest defences and tightest controls on the assets that, if compromised, would result in a substantial financial loss or physical danger. This means that in the event of a perimeter compromise, your primary critical workloads remain protected.
Key Statistics: The Cost of Insecurity
Understanding the financial and operational risks is key to securing the budget for hardening efforts.
| Metric | Statistic | Source |
| Median Dwell Time | 10 Days (down from 16 in 2022) | Mandiant M-Trends 2024 |
| Zero-Day Usage Growth | >50% increase in 2023 vs 2022 | Mandiant M-Trends 2024 |
| Avg. Cost of Industrial Data Breach | $5.56 Million | IBM Cost of a Data Breach 2024 |
| Cost of Unplanned Downtime | ~$125,000 per hour | ABB Value of Reliability Survey |
V. Proactive Mitigation
Don’t wait until there’s a breach to act. Defending against such threats today includes measures such as application allowlisting applied with a defense-in-depth approach.
This is when an Application Control Engine becomes necessary. If you set up your systems so they’re only running apps that are trusted and pre-approved, you can essentially stop zero-day malware cold. And even if an exploit lands on a server, the malicious payload will not execute because it is not on the allowlist.
VI. Simplify Complexity
Complex networks like this are a playing field for bad actors. Superfluous software and open ports only extend your attack surface for zero-day threats to land.
Simplify your environment by:
- Disabling unused ports and services.
- Removing unnecessary software.
- Segmenting networks to contain key operational technology (OT) from corporate IT.
If an important system doesn’t need internet access to operate, then pull it. Simple means less attack surface area for the bad guys.
VII. Automation
And it’s faster than a human being can react in this fast-paced modern world of cyberattacks. Automation is the equalizer. IBM says those organizations which had heavily invested in security AI and automation saved $1.9 million on data breach costs compared to their less strategic counterparts.
Automate patching with threat detection and response. By eliminating manual latency, you eliminate the window of compromise and are able to enforce your security policies 24/7.
Conclusion
Infrastructure hardening is not a project but an ongoing effort. Following these seven principles, ranging from visibility and standardization to proactive automation, creates a defense that can stand up to the unknown. Begin analyzing your critical assets today to stay resilient against the next generation of zero-day threats.
