Cybercriminals are opportunists who are always looking for ways to exploit weaknesses in business systems. Sometimes those weaknesses are brand new and have no known fix.
Other times, they are well-documented flaws that simply have not been patched. Whether they are zero-day vulnerabilities or known vulnerabilities, both create an open door for attackers.
The longer a vulnerability remains unaddressed, the greater the chance it will be used against your business. Even a short delay can give attackers the opportunity to gain access, disrupt operations, and compromise sensitive data.
In this article, we spoke with Francois Goosen, Centralized Services Lead at Intelligent Technical Solutions (ITS), to help us break down:
- What is a zero-day vulnerability and a known vulnerability?
- What are the differences between zero-day and known vulnerabilities?
- Why are zero-day vulnerabilities and known vulnerabilities dangerous?
- What should you do about them?
After reading, you will understand why both are dangerous, as well as know what steps you should take to protect your organization.
What is a Zero-Day Vulnerability?
A zero-day vulnerability is a security flaw that is unknown to the vendor or the public before it is exploited. The term "zero-day" means the vendor has had zero days to fix the issue before it is used in the wild.
Zero-day vulnerabilities are especially dangerous for three reasons:
- No existing patch
Since the flaw is new, the vendor has not yet developed a fix.
- Difficult to detect
Security tools may not yet recognize the exploit, allowing it to bypass defenses.
- Targeted use
Attackers often use zero-days to target high-value organizations or specific industries.
Francois pointed out the urgency of responding to these types of vulnerabilities:
"Zero days are even worse because you could be compromised at that point, and the longer you wait, the longer your systems will be vulnerable."
Zero-days require immediate attention. Even without a patch, organizations must implement temporary mitigation strategies to limit exposure.
READ: Follina Zero-Day Exploit Allows Attackers to Execute Remote Code
What is a Known Vulnerability?
A known vulnerability is a flaw that has already been discovered and documented. In most cases, the vendor has released a patch or update to fix the issue. The danger comes when organizations delay or fail to install the update.
Known vulnerabilities are a favorite target for attackers because they can easily find lists of these flaws and scan the internet for systems that have not been patched. Once they find one, exploitation can be quick and automated.
Why Both Zero-Day and Known Vulnerabilities Are Dangerous
Although they differ in how they are discovered and addressed, both zero-day and known vulnerabilities can lead to severe consequences.
“You need to jump on both of those promptly,” Francois says. Because while zero-day vulnerabilities can be more dangerous, both often lead to serious security breaches.
Zero-Day Risks
- Give attackers a head start before defenses can be updated.
- Often used in highly targeted, high-impact attacks.
Known Vulnerability Risks
- Widely documented and easily exploitable with public tools.
- Usually a sign of poor patch management when left unaddressed.
The Business Cost of Unpatched Vulnerabilities
Unpatched vulnerabilities can cost a business far more than the time it takes to update a system. The risks include:
- Financial Loss – This includes direct costs such as ransom payments and recovery expenses, as well as indirect costs like lost revenue during downtime.
- Reputational Damage – Clients lose trust when sensitive data is compromised.
- Compliance Penalties – Many industries have strict security regulations such as HIPAA, CMMC, or PCI DSS, and non-compliance can lead to heavy fines.
- Operational Disruption – Every hour of downtime can result in significant productivity losses.
What Should You Do to Combat Zero-Day Vulnerabilities?
Here are the things you need to do to address the risks:
1. Implement a Proactive Patch Management Program
One of the most common reasons businesses fall victim to known vulnerabilities is a lack of timely patching. Attackers often scan the internet looking for unpatched systems, and if your business is on that list, you are a target.
A proactive patch management program should include:
- Scheduled updates: Apply patches as soon as possible, ideally within days of release for critical vulnerabilities.
- Asset inventory: Maintain an up-to-date list of all hardware, software, and operating systems so nothing gets overlooked.
- Testing process: Test patches in a controlled environment before rolling them out to production systems to avoid operational disruptions.
- Automated patching tools: Use endpoint management software to ensure consistency across all systems, including remote devices.
- Patch verification: Confirm that updates have been successfully applied, rather than assuming they have.
2. Develop a Zero-Day Response Plan
Zero-day vulnerabilities present a unique challenge because there is no fix available when the flaw is discovered. In these situations, speed and coordination are critical.
A strong zero-day response plan should include:
- Vulnerability monitoring: Subscribe to trusted security advisories from vendors, security researchers, and agencies like CISA.
- Temporary mitigations: Disable vulnerable features, restrict access to affected services, or isolate high-risk systems until a patch is released.
- Incident response playbooks: Document specific steps to follow depending on the type of vulnerability, so your team is not making decisions under pressure.
- Enhanced monitoring: Increase log analysis, intrusion detection, and anomaly detection on potentially affected systems.
- Vendor communication: Work directly with the affected software or hardware vendor for status updates and mitigation guidance.
Even though zero-days are unpredictable, having predefined processes can significantly limit the damage.
3. Partner with a Trusted MSSP
Managing vulnerabilities and responding to threats in-house requires specialized skills, 24/7 monitoring, and dedicated resources. For most organizations, this is both costly and difficult to sustain.
Partnering with a Managed Security Service Provider (MSSP) like ITS gives you:
- Continuous monitoring: Around-the-clock detection of threats and suspicious activity.
- Patch management expertise: Automated patch deployment combined with human oversight to address exceptions and special cases.
- Rapid response capabilities: MSSPs can contain incidents quickly before attackers have a chance to escalate their access.
- Scalability: As your business grows, an MSSP can adapt the level of protection without requiring major investments in additional staff or tools. To put things in perspective, Francois shares "we are patching around 20,000 Windows endpoints monthly. That is at least 250,000 patches a year."
4. Train Staff on Security Awareness
Even the best technical defenses can be undermined by human error. Employees need to understand that applying updates is not just a technical task, it is a business safeguard.
Effective security awareness training should cover:
- Why updates matter: Explain in plain language how delaying an update can give attackers an opportunity.
- Recognizing suspicious activity: Teach staff how to spot signs of compromise, such as unusual login attempts, pop-up warnings, or sudden system slowdowns.
- Safe update practices: Ensure remote workers know how to update their devices securely, even when working outside the office network.
- Incident reporting: Create a clear process for employees to report issues immediately without fear of blame.
When staff are engaged and understand their role in security, the entire organization becomes harder to compromise.
Ready to Protect Against Zero-Day and Known Vulnerabilities?
Zero-day and known vulnerabilities both represent serious security threats. Zero-days are dangerous because they are unknown and unpatched when discovered. Known vulnerabilities are dangerous because they are often ignored or left unpatched, making them an easy target.
Whether a flaw is new or well-documented, your response time can be the difference between business as usual and a full-blown security incident.
With ITS’s proactive patching and vulnerability management, your business gains a strong defense against both types of threats before they become costly breaches. Take the first step toward closing the gaps in your IT security. Schedule a vulnerability assessment with us today.
You can also check out the following resource for more info:
- Best Practices to Keep Software Updated for Your Business
- How to Protect Your IT Network (& Why Antivirus Isn’t Enough)
