Why Zero-Day Attacks Bypass Antivirus (And How To Protect Your Business)

Traditional antivirus software used to be enough to detect and protect against most cyber threats, but the rise of zero-day attacks has now changed that. Zero-day attacks exploit new security vulnerabilities before developers have a chance to fix them, which gives cybercriminals just enough time to strike. The financial impact of these attacks can be huge, as the average breach now costs U.S. businesses $10.22 million, and zero-day attacks have accounted for about a third of these breaches so far in 2025. The limitation of traditional antivirus software is that it relies solely on known threat signatures, which means it’s powerless to detect and stop new, unknown threats. Fortunately, endpoint detection and response (EDR) is a useful solution. It can proactively identify and stop new threats in real time, so businesses find it easier to keep their devices and networks safe and secure.

Signature-based detection can’t keep up with zero-day threats

To get a handle on where traditional antivirus protection falls short, you first need to understand the signature-based detection it relies on. This is basically an automatic scan that checks executable files, documents, and programs against a list of known threats like viruses, ransomware, rootkits, and the like. These are generally threats that cybersecurity professionals have already discovered, and have often already released a fix for. This means traditional antivirus software is reactive as it only detects threats that are already known, and doesn’t know how to proactively look out for and defend against new ones. 

The problem is that hackers are constantly searching for new vulnerabilities to exploit, which means they may stumble upon zero-day flaws that haven’t been discovered or protected against yet. When cybercriminals find a new weakness, they also tend to move fast: a recent Google report found it takes an average of just seven days for hackers to publish a way to exploit a security vulnerability once it’s been discovered. So, as a result, new zero-day threats that aren’t already in the antivirus database can easily slip past detection, and then successfully damage the network or endpoints (which includes laptops, computers, and servers).

EDR proactively catches (and stops) new threats 

In contrast to traditional antivirus software, endpoint detection and response (EDR) continuously monitors endpoint devices and network activity for suspicious activity as and when it happens — whether it matches a known threat signature or not. If a threat is detected, EDR tools also quickly isolate the infected device right away to stop it from spreading. As 90% of successful cyberattacks now start at endpoints, EDR is essential to provide proactive protection against threats that antivirus software simply can’t catch. So, what exactly should you look for in an EDR provider? The top EDR solutions typically use intelligent threat detection to reduce false alarms. This feature should ideally have been developed and refined by cybersecurity professionals, and accurately tell the difference between harmless glitches and real malicious activity. This means you only respond to genuine threats, which helps avoid pointless disruptions and saves time in the process. 

Patch management closes zero-day gaps

Most zero-day vulnerabilities get targeted before a patch is released or just days after. And it gets worse: 68% of cyberattacks take advantage of flaws that already have patches, but haven’t been applied yet. This is why it’s so important to keep your software updated with the latest patches. Fortunately, this is something patch management software can help with. This tool scans for available patches and installs them automatically, either in real-time or on a schedule, across all devices. In fact, many EDR solutions also take care of patch installation automatically, so this is another feature to look for. On top of that, patch management software can also detect when an installed patch doesn’t work as expected. It will then either return the system to how it was before or reinstall the patch to solve the issue.  

Zero-day attacks are on the rise, and traditional antivirus software is simply no match for them. To better protect themselves, businesses can use EDR together with patch management software. These tools can help you stay ahead of attackers, and keep your networks and devices safe from both known and unknown threats.