What Is a Zero-Day Attack?

Written by Kelsey Kinzer on July 5, 2022

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When writing long stretches of code, it’s easy to make a mistake. That’s what pair programming, error handling, and logging are for.

But those methods don’t always uncover every mistake. And sometimes, hidden errors can lead to enormous consequences, like zero-day attacks. In a zero-day attack, cyberattackers exploit an unseen vulnerability before engineers can even recognize what’s happening, let alone stop it. In other words, the developers are already behind: they have “zero days” to fix the problem.

As you can imagine, zero-day attacks can hurt companies financially and reputationally, so it’s important to be and stay vigilant. In this piece, we’ll explain how zero-day attacks occur, who is at risk of these attacks (hint: everyone), and offer some tips to prevent zero-day attacks from inflicting damage on your organization.

Zero-Day Definitions

Zero-day attacks are often conflated with zero-day vulnerabilities and zero-day exploits, but all three terms have distinct meanings. To get on the same page, let’s walk through each definition below.

Zero-Day Vulnerability

A zero-day vulnerability is an unknown software, firmware, or hardware flaw. Because vendors and clients aren’t aware that a zero-day vulnerability exists, they don’t take steps to minimize its risk. Until they are exploited, zero-day vulnerabilities typically remain undetected.

Zero-Day Exploit

A zero-day exploit is the method cyberattackers use to take advantage of a zero-day vulnerability. Zero-day exploits occur in different ways depending on the vulnerability an attacker is targeting.

Zero-Day Attack

Zero-day attacks arise when hackers use vulnerability exploits to gain access to a system. At that point, attackers have free rein 一 they can access confidential data, sensitive banking information, customer files, or other high-value resources.

How Do Zero-Day Attacks Work?

Now that you know what zero-day vulnerabilities, exploits, and attacks are in theory, let’s go through an example of how zero-day attacks work in practice.

Every attack is different, but most go something like this:

  1. Developers inadvertently create an operating system with a zero-day vulnerability in it.
  2. A threat actor is actively looking for a vulnerability in that system and spots it.
  3. The attacker begins writing malicious code (otherwise known as “exploit code”) to execute an attack.
  4. A breach occurs, which can go on for several hours, days, or weeks.
  5. The public or security analysts finally realize an attack is happening.
  6. Software engineers create a security patch as fast as possible.


It’s important to note that the person who discovers a zero-day vulnerability isn’t always the same person who carries out an attack. Someone may pick up on a vulnerability, steal information, and then sell it on the dark web. Other attackers can use that information to design sophisticated phishing schemes, social engineering campaigns, computer worms, or malware that further harm your company.

Who’s at Risk of a Zero-Day Attack?

As we hinted at the beginning of this post, any organization is susceptible to zero-day attacks.

Even security companies aren’t impervious to zero-day attacks. In 2011, cyberattackers found a vulnerability in Adobe Flash Player that eventually granted them access to RSA’s network. They sent emails to employees with malicious attachments containing a remote administration tool. With employee-level access, the hackers stole sensitive information related to RSA’s two-factor authentication products.

Unfortunately, these attacks continue to get more prolific over time. In 2020, Zoom suffered a zero-day attack due to a vulnerability in their platform. If Zoom users were running on an old version of Microsoft Windows, hackers could access their computer 一 and all the files in it 一 remotely. According to the Ponemon Institute, 48% of organizations experienced a data breach over the past two years, and 62% of those companies were not aware of the vulnerability prior to the full-blown attack.

How to Prevent Zero-Day Attacks

Zero-day attacks can have terrible repercussions for companies and their customers, but the good news is that you can take steps to reduce your company’s risk, such as the ones described below.

Workforce Education

One of the best ways to prevent zero-day attacks is by teaching your employees cybersecurity best practices and what to do in case of a breach. Educating users on the telltale signs of phishing and social engineering campaigns will increase the chances of identifying threats and then escalating them to the right people.

BYOD Policies

Strict Bring Your Own Device policies are essential in preventing zero-day attacks, especially as more and more companies go fully remote. Employees’ personal devices do not have the same protections as network devices do and are more likely to be targeted by bad actors.

Vulnerability and Patch Management Strategies

Strong vulnerability and patch management are key to zero-day attack prevention. Vulnerability management lessens a company’s exposure by periodically unearthing, tracking, and repairing vulnerabilities in an organization’s software and hardware. Patch management enables companies to test, implement, and confirm that patches are working. When both of these processes are working in tandem, it’s much tougher for attackers to find and exploit vulnerabilities.

Zero Trust Architecture

The idea behind Zero Trust security is that no one is to be trusted, and a user’s identity must be verified at all stages of their interaction with a company network. In that way, Zero Trust architecture greatly decreases the opportunity for bad actors to pinpoint vulnerabilities and infiltrate a company’s systems. To penetrate a Zero Trust architecture, attackers must circumvent significant hurdles like network segmentation, least privilege access, and multi-factor authentication.

Incident Response Planning

Attacks happen, no matter how many precautions you have in place. To that end, you need a robust incident response plan to minimize the devastating effects of an attack. Security teams should know this plan inside and out and test its efficacy often.

Secure Your Data by Patching Vulnerabilities

We know that zero-day attacks are insidious and can have devastating financial and reputational consequences. But constantly monitoring, discovering, and remediating those vulnerabilities can be extremely challenging.

JumpCloud’s Patch Management solution changes all that, providing visibility into the state of your browsers, applications, and device operating systems and giving your IT team the tools they need to automate patch development and deployment. 

Admins can easily manage device patching from a single console, reinforcing security posture, and maintaining organizational compliance in a streamlined, systematic way. Learn more in Introducing JumpCloud Patch Management.

Kelsey Kinzer

Kelsey is a passionate storyteller and Content Writer at JumpCloud. She is particularly inspired by the people who drive innovation in B2B tech. When away from her screen, you can find her climbing mountains and (unsuccessfully) trying to quit cold brew coffee.

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