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What Is Zero-Day Vulnerability? Zero Days Explained

March 22, 2022

By Peter Barnett

A zero-day vulnerability can cause serious problems for businesses, as well as for software users. If these vulnerabilities are hacked or exploited, unauthorized individuals or automated devices can gain access to restricted system areas or software data stores. This is why a thorough approach to software patches — both from the software developer’s side and from the end user’s side — is crucial in cybersecurity and data protection.

Zero-Day Definition: What Is a Zero-Day Vulnerability?

How do we define zero-day vulnerabilities? A zero-day vulnerability refers to an area of weakness within a system or a piece of software that has not yet been corrected or patched. There are two fundamental types of zero-day vulnerabilities:

  • Known zero-day vulnerability — The software developers know about the vulnerability and are in the process of developing a patch to fix this. Or, the software’s users have identified a vulnerability and are in the process of informing the developers.
  • Unknown zero-day vulnerability — The software developers or users have not yet identified the vulnerability, so there is no patch currently in development. If malicious entities and cybercriminals do know about the vulnerability, this will still be classed as unknown because it is not known to the developers, even if these malicious entities are in the process of exploiting the flaw.

What Are Zero-Day Hacks or Exploits?

While zero-day vulnerabilities describe what happens when issues are left unpatched and systems are left exposed, this is not a problem for businesses all by itself. Instead, the danger begins to arise when malicious actors and cybercriminals exploit these vulnerabilities.

Exploiting a zero-day vulnerability basically means using the exposed area of the system to gain unauthorized access. While a patch should prevent this access, it cannot provide protection if it is not deployed or — in the worst case — if the patch has not been developed because the vulnerability has not yet been identified.

The concept of hacking a zero-day vulnerability may be synonymous with that of the zero-day exploit described above, or it may refer to a more sophisticated attack on the vulnerability. Hacking is generally considered to mean “manipulating computer systems to bypass access and authentication protocols” rather than simply gaining access to a system because those protocols are not in place. However, the end result is the same whatever the definition — an unauthorized individual or device gains access to systems and data.

High-Profile Zero-Day Attacks from Recent Years

To understand more about how damaging these attacks can be, both to businesses and to their customers, let’s take a look at someday zero attack examples. We’ve compiled a list of some of the highest-profile zero-day exploits from the last decade to provide additional insight into the scale of the problem.

Zero-Day Attack

LinkedIn Zero-Day Attack
Alibaba Group's Taobao Retail Platform Zero-Day Attack
Facebook Zero-Day Attack
Marriott International Hotels Zero-Day Attack
Yahoo Zero-Day Attack

Date of Attack

June 2021
November 2019
April 2021
September 2018
August 2013

Scale of Attack

Records of 700 million users were left exposed, or over 90% of LinkedIn's user database. The vulnerability is thought to have been accessed via the Safari web browser.
1.1. billion "pieces of data from user accounts" were potentially exposed for up to eight months before the vulnerability was detected. Around 20 million user accounts had been exposed in a similar attack just over three years previously.
More than 530 million user accounts were exposed, and personal identification and contact information was posted on public websites. The same vulnerability was later used to expose and leak data from over 540 million user accounts, underling how dangerous unpatched vulnerabilities can be.
Registered accounts of over 500 million guests were exposed and data were stolen. The vulnerability was possibly exploited for more than four years before detection, with links to foreign intelligence groups.
More than 3 billion user accounts were left exposed. Details of the attack were not released for three years, and the incident remains perhaps the most serious on record.
It is important to remember that these examples represent just a few of the numerous zero-day attacks that have taken place in recent years. There are many more examples — generally of a lower profile but damaging nonetheless.

In addition, you need to consider how we define a zero-day exploit — i.e., a zero-day vulnerability that is identified and exploited by malicious actors before it is patched. With this in mind, it becomes clear that there are many other zero-day vulnerabilities that have not yet been exploited but still represent a significant danger to businesses and to general users.

Protecting Your Business Against Zero-Day Exploits

How do you protect yourself and your business against zero-day vulnerabilities? How do you make sure that your business systems are not exposed? Here are a few things to bear in mind as you shore up your defenses:

  • Monitor and manage any abnormalities — Abnormal user behaviors or analytics data could provide an indication that a vulnerability exists in the system.
  • Communicate the danger to all team members — Make sure all of your team members are engaged in the need to protect systems and promote widespread vigilance.
  • Implement patch management solutions — These solutions will help you to ensure that patches are identified and deployed without delay, minimizing the potential for vulnerability.
  • Utilize deployment software tools — This set of tools assists your business as you implement and assess software deployments across multiple endpoints from one centralized location.
  • Put remote assistance software in place — Ensure that all users have support and assistance across remotely deployed devices and desktops, utilizing software solutions to make remote support effective and immediate.

Protect Your Business from Zero-Day Bugs and Vulnerabilities — Put Action1’s Services and Solutions on the Case

Here at Action1, we provide a range of software solutions and services designed to help businesses protect their systems and devices in the face of a wide range of different threats. These offerings include remote monitoring and management, which work to ensure businesses can guarantee the right levels of protection on an organization-wide basis. 

Action1’s solutions can even offer protection when the situation may seem outside of internal control, such as in the case of zero-day vulnerabilities. With Action1’s patch management services on your side, you can ensure that patches are deployed automatically as soon as they become available, and vulnerabilities are not permitted to expose your systems. Reach out to our team today to learn more, or try these solutions and services for yourself to discover how they fit with your own business structure and strategy.

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