Updated: Aug 11, 2026 By: Marios
Zero-day vulnerabilities are undiscovered weaknesses in software, hardware and firmware. Finding them before malicious attackers is paramount to the safety of your business.
Estimates are that across the globe, around 4000 cyber attacks happen every day. This figure could be higher, as many go unreported. Of businesses hit by cyber attacks, 52% of them lose more than 5% of their total revenue. This makes security essential, and one of the most critical is the preparation for zero-day vulnerabilities. These are weaknesses you don’t even know exist, making their appearance an issue of when rather than if.
What is Zero Day?
Zero-day vulnerabilities describe an unknown or unresolved security flaw that exists in a product. This means that those developing or maintaining the systems have ‘zero’ days in which to make a fix if it is found and exploited. By this time, the software, hardware or firmware will have already been compromised.
These vulnerabilities exist from the moment a piece of software or hardware is released. At this point, no one will even know the issue exists. It could be hours, weeks, months or years until it is discovered. The best outcome is that it is found by someone who can repair it, with the worst case being it is discovered by threat actors first.
It is very rare that whoever finds them first does not make them public. Owners do this so that updates can be rolled out, and consumers can take the action they need to safeguard themselves. In some cases, communities of criminals may circulate the weakness amongst others in their fraternity.
Finding a Zero Day Vulnerability
No system is impervious to weakness. Any sector, industry, software package or developer can have vulnerabilities within them. Once this is accepted, it is easy to understand how to spot and deal with issues when they arise. This allows an organisation to react and deal with the situation as best as possible.
When this does happen, action must be swift; a patch must be created to solve the issue. Any companies or customers who may be impacted must then be notified, updating the patch as soon as it becomes ready. There is a chance they may already have been compromised, so giving them advice on how to look for breaches and safeguard their systems is also crucial.
The Most Famous Zero Day Attacks
One of the most famous zero-day attacks, which literally changed the world, was the 2010 Stuxnet attack. This infiltrated centrifuges used to enrich uranium in Iran. It shut down their facilities by using several openings in Windows, sabotaging Siemens PLCs. Suddenly, geopolitics was now the domain of zero-day attacks, and everything from water supplies to transportation had to make cybersecurity a key principle.
Another was the 2014 Shellshock exploit. For 20 years, the code in the Unix/Linux command shell has remained solid. When exploited, the IoT was opened, causing millions in damages. It also showed just how dangerous the use of old tech that has not been updated can be.
Defending Against Zero Day Attacks
Defending against these attacks is tough. This is because the weaknesses are not known in advance. These attacks won’t show up on traditional anti-virus and signature-based tools, as the latter only matches known malicious patterns against incoming activity. This is why behavioural threat detection is more important, which looks for suspicious patterns that don’t usually occur. This could include accounts accessing data they have never needed before, or connecting to unknown servers outside usual hours.
Network detection tools follow a similar method and are also key. They will monitor for communication patterns which seem out of the ordinary. This can cover unmanaged devices, though it does become obscured by encrypted traffic.
A further method is to actively hunt out threats before someone else discovers them. This does require expert knowledge, but there are analysts that can proactively search for indicators of weakness in systems. This human approach can often help find what automated procedures can overlook.
Lastly, having a team that is ready to create patches immediately is vital. Once a vulnerability is found, they must fix it and do so against the clock. This allows for the rapid deployment of security updates. The downside is that while it fixes issues that have been found, unknown ones still remain.
The Increasing Threat of Zero Day Attacks
Unfortunately, these attacks are not subsiding, but are getting worse. As the internet of things expands and the connected nature of the world gets larger, so are its weak points. As the world has moved towards remote work, the situation has also been exacerbated.
It is not all doom and gloom, though. Fixing these has become better, and proactive organisations can limit the damage. This allows them to continue to build trust with their clients and customers, even in the event of an attack.
