A Growing Concern in Cybersecurity – Communications of the ACM

Zero-day vulnerabilities are hidden security flaws in software or hardware that developers don’t yet know about. The term “zero day” highlights the urgency—there are zero days to fix the issue before attackers can take advantage of it.¹

Zero-days create a race between attackers and defenders. The moment an exploit becomes known, developers scramble to release a patch, but until then, traditional defenses are largely ineffective.

Antivirus programs, firewalls, and endpoint detection tools often rely on known signatures. Without one, zero-day attacks slip through undetected. They don’t always leave visible traces—systems can be compromised quietly, while attackers escalate privileges, harvest credentials, or install persistence mechanisms. That’s why the demand for specific STEM careers that can detect fraud manually has grown.

Though high-profile government systems and enterprise infrastructure are frequent targets, small and mid-sized organizations are equally at risk—especially if they rely on widely used software or legacy systems. In fact, it’s the ubiquity of these tools that makes them such attractive entry points.

Zero-days are not confined to a single layer. They can exploit weaknesses across various parts of the tech stack. Here’s where they typically strike:

Browsers, email clients, and document readers are often entry points. These tools frequently handle untrusted content and are vulnerable to malicious file types or websites. For example, several Chrome and Microsoft Office zero-days have been linked to phishing campaigns and drive-by downloads.

Targeting the operating system or its kernel can yield administrative control—opening the door to remote code execution or full system compromise. Notably, the EternalBlue exploit led to the global WannaCry ransomware outbreak by leveraging a Windows protocol vulnerability.²

These attacks strike low-level components like UEFI firmware or graphics drivers. Because these systems run beneath the OS layer, the attacker can stay hidden for a long time—even if you reinstall your system. That makes them difficult to detect and remove unless you use a generative AI solution that can automate these tasks.

Some advanced threats go beyond data theft or access control, targeting hardware behavior itself. For instance, attackers can exploit firmware to induce CPU throttling, degrading system performance and masking malicious activity.

Zero-days are not just theoretical—they’ve been exploited in major cybersecurity incidents. Let’s examine a few examples:

This exploit targeted a widely used driver to gain SYSTEM-level privileges. Before Microsoft could issue a patch, attackers used it to install a rootkit on targets’ computers.³

What could’ve helped: Organizations can reduce risk by blocking untrusted drivers using Microsoft Defender Application Control and conducting regular audits to remove outdated or unsupported components.

This high-severity vulnerability in Chrome’s JavaScript engine allowed attackers to achieve remote code execution by exploiting heap corruption. Delivered through specially crafted HTML pages, the exploit was observed in the wild before a patch became available. It affected both desktop and Android versions of Chrome.⁴

What could’ve helped: Enforcing browser isolation policies, content security policies, and DNS filtering would have reduced exposure, even before a patch was available.

The Windows Print Spooler vulnerability allowed attackers to run malicious code with full system access. By exploiting this flaw, attackers could install programs, view, change, or delete data, and even create new accounts with full user rights.⁵

What could’ve helped: Disabling the Print Spooler on devices where printing wasn’t required—especially servers—could have blocked exploitation. Proactive hardening of legacy services remains a vital defense strategy.

While you can’t prevent zero-day exploits from existing, you can significantly limit their impact:

Cloud Email Security Services

Cloud Email Security Services protect businesses from email-based threats like ransomware and phishing attacks. They use advanced threat detection to scan incoming and outgoing emails for malicious content, suspicious attachments, or phishing links. Behavioral analytics and machine learning help identify risks early and prevent threats from escalating. These cloud-based solutions stay updated with new attack methods, including zero-day vulnerabilities, ensuring businesses remain protected against evolving threats.

Apply updates as soon as they’re released—especially for applications with Internet exposure or deep system access. Modern automated patching tools reduce human delay and help ensure consistency across distributed environments. Speed is critical: many zero-day exploits are weaponized and deployed within hours of discovery. A strong patch cadence limits the attack window.

Outdated or unsigned drivers are common targets for low-level exploits, especially in privilege escalation attacks. Implement driver allowlisting, verify digital signatures, and use secure boot protocols to validate firmware integrity at startup.

Regular driver updates also help close security gaps in third-party hardware components before they become attack vectors. To streamline the process, consider using a driver updater to automate scans and installations. It’s especially helpful across large device fleets where manual updates are impractical.

Zero Trust eliminates the assumption that internal traffic is safe. Every device, user, and request must undergo continuous authentication and authorization. This framework checks every access point at every stage, which greatly shrinks the attack surface and blocks attackers from moving deeper into the system—even if they get in through a zero-day vulnerability.

Grant users and processes only the minimum permissions required to perform their tasks. Combine this with network segmentation and role-based access controls to reduce the blast radius of a compromise. If malware rides in on a zero-day, it shouldn’t have admin-level access to your entire system.

Traditional antivirus tools rely on known signatures and are ineffective against new exploits. Instead, advanced Endpoint Detection and Response (EDR) platforms use behavioral analytics to detect anomalies. This includes monitoring unexpected processes (e.g., PowerShell spawning) or unusual user activities (e.g., accessing large volumes of data after hours). These anomalies can flag a zero-day exploit even before it’s classified.

Device Security and Maintenance

Zero-day attacks frequently target endpoint devices first. To protect against attacks, implement remote wipe capabilities, robust authentication, and full-disk encryption. Keeping operating systems and software up to date also helps close vulnerabilities before they can be exploited.

You should also secure your devices with malware protection. Consider managed detection and response services or EDR solutions to provide rapid threat response at the enterprise level. Additionally, security tools like MacKeeper can help with malware detection and privacy protection and establish a baseline across personal and organizational devices.

No technical control can fully replace user awareness. Human error remains a leading factor in initial compromises, which is why enrolling employees in cybersecurity online bootcamps is so valuable. Ongoing training from these programs helps staff recognize phishing attempts and social-engineering tactics that often deliver zero-day payloads. Paired with clear incident-reporting procedures, this education creates a powerful human firewall around your organization. Educating staff on using secure software is crucial for organizations of any size.

For those interested in learning IT security in a structured way, enrolling in online IT diploma courses can be an effective path to building expertise and enhancing cyber resilience.

Zero-day vulnerabilities remain one of the most critical cybersecurity risks. As businesses adopt cloud services, IoT devices, multiple multimedia files, and remote work environments, their exposure grows, offering more opportunities for exploitation. At the same time, attackers are adapting, refining their tactics, and continuously searching for new vulnerabilities to exploit.

While the risks remain significant, there are proactive steps organizations can take to mitigate their impact. Regular system updates, a layered defense strategy, and constant awareness of emerging threats are essential. A proactive, continuous approach to cybersecurity is key to protecting systems from the evolving threat of zero-day exploits.

1. IBM. What is a zero-day exploit? IBM Think Blog. https://www.ibm.com/think/topics/zero-day

2. HYPR. What Is EternalBlue? https://www.hypr.com/security-encyclopedia/eternalblue

3. Help Net Security. 0-day in Windows driver exploited by North Korean hackers to deliver rootkit (CVE-2024-38193). Published August 20, 2024. https://www.helpnetsecurity.com/2024/08/20/0-day-in-windows-driver-exploited-by-north-korean-hackers-to-deliver-rootkit-cve-2024-38193/

4. Cyble. High-Risk CVE-2024-7965 Vulnerability in Chrome’s V8 Engine Requires Quick Fix. https://cyble.com/blog/high-risk-cve-2024-7965-vulnerability-in-chromes-v8-engine-requires-quick-fix/

5. Microsoft Security Response Center. CVE-2021-34527 | Windows Print Spooler Remote Code Execution Vulnerability. https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34527

Alex Tray is a system administrator and cybersecurity consultant with 10 years of experience. He is currently self-employed as a cybersecurity consultant and as a freelance writer.