What Is A Zero-Day Vulnerability and How Does it Work?

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Understanding Zero-Day Vulnerability

There’s no end to the numerous challenges involved in securing your networks, systems, and environment. Whether it’s ransomware, social engineering or data theft, the volume of cyber threats that impact IT assets, personal data, and business networks are staggering. This is especially the case with “zero-day vulnerabilities.” Because cybersecurity is reliant on updates and the latest patch to protect against malicious attacks, zero-day vulnerabilities are dangerous periods for organizations. But what does this phrase specifically mean?

Essentially, zero-day vulnerabilities refer to an app, program, or software which hasn’t received the latest update from its vendor. Because of this, outdated apps are filled with loopholes exploitable by malware. However, even if a vulnerability exists, it does not mean an exploit also exists. Said vulnerabilities are normally addressed before they are widespread problems. Though, the longer a vulnerability remains, the likelier it will lead to the development of an exploit.

The history of zero-day vulnerabilities is a long and fascinating one. Some exploits were developed as simple attack tools for disrupting programs, others were exceptionally complex and developed for espionage and damaging infrastructure. In this article, you’ll get a better idea of what they are, how they occur, and what you can do.

Generally, there are three ways to look at the “lifespan” of a zero-day problem.

Zero-day Vulnerability 

The vulnerability discovered due to outdated software or other unintended issues. It’s referred to as “zero day” since there have been zero days since the release of a fix.

Zero-day Exploit

The malicious code developed to cause unintended problems in the vulnerable software/system.

Zero-day Attack

The release of the code, targeting the vulnerable software.

Generally, once the vulnerability is discovered the vendor is informed of the problem. This process is often not disclosed to the public to reduce the risk of widespread exploits. After the discovery of the vulnerability, fixes are released afterward.

Often, vulnerabilities and exploits are developed by coordinated attackers with an in-depth understanding of coding. Therefore, they should not be taken lightly.

What is targeted?

Malicious attackers are always on the prowl for vulnerabilities, so it’s worth understanding what they target. Among the most common vectors for zero-day vulnerabilities are websites.

Compromised websites are perfect vectors since they’re widely used. They’re additionally dangerous because a vulnerable website may not indicate malicious behavior. In other words, the host is infected with the zero-day exploit but doesn’t know it.

Software and apps which rely on personal information are also targeted. The more valuable the login, the likelier malicious parties look to create an exploit. Once infected, users can give away personal data and records which allows malicious parties to penetrate systems, allowing them to steal information and cause damage with a virus.

In other cases, operating systems are the target, where the goal is to force unusual behavior and service disruption.

The severity of the issue depends on the vulnerability level and exploit. Because it targets an operating system, damage can be catastrophic and lead to severe service disruptions. For an individual user, this may lead to the re-installation of the OS itself.

What are the risks?

Until fixed, there are higher chances third-parties will look to exploit vulnerabilities, resulting in the “zero-day exploit.” Once created, the exploit is released as a script or form of malware causing performance problems in software and operating systems.

The risks involve loss of personal information, loss of essential services, deletion of files, infection of other systems (if on a business network), permanent damage to IT infrastructure, and downtime.

The longer the vulnerability exists, the likelier an exploit will surface, leading to the problems listed. It’s a scenario no individual or organization wants to deal with, but an unfortunate reality.

How can I protect my data?

Shielding valuable info is a priority. But without a patch to stop an exploit, what can you and your enterprise do to reduce data-loss risk? While it’s important to update all targeted software as soon as possible, there are several things you can do to mitigate potential damage.

You can first contact the vendor(s) and request a timeline of when a patch is expected to release. While not definite, it can give you an idea of what to expect and how long to use specific security practices.

It’s also good to make sure other software is updated to the latest version, especially anti-malware software.

Even though your anti-virus solution may not have a response for a zero-day exploit, it can help reduce system damage by identifying dangerous behavior in an infected system. It may also allow you to detect other forms of malware related to the exploit, keeping the problem contained.

If the software used by an organization is vulnerable, inform staff of the issue. If possible, it’s best to terminate use of the app while a patch is worked on, mitigating risk.

However, if the vulnerability relates to an operating system or essential service, limit usage of the vulnerable systems. For example, you may need to prohibit the use of specific functions in an OS if the OS is targeted.

It’s also advised to make good use of a versatile firewall. Firewalls can shut off points of access in a network. This means if a system is infected, it’s identifiable and closed off to prevent further spread of the infection. While it does not stop the zero-day attack, it can help reduce the potential damage.

One other important practice is maintaining good security policies. Not just on an individual level, but for staff too. This encompasses a  lot of things, such as how staff proceeds after an identified zero-day vulnerability.

What programs are they allowed to access and, what features? Can they still communicate via email? What essential services are accessible to them? Questions like those fall under good security documentation and can help reduce damage to your infrastructure.

What if I’m affected?

Even with best intentions and a savvy team of IT experts, it’s possible to fall victim to a zero-day attack. While most vulnerabilities are detected and patched within a short time-frame, there are instances where you don’t have the latest version when needed.

In these scenarios, it’s important to respond as quickly as possible to mitigate downtime. Identify the infected system(s) and disconnect them from all networks, so the exploit doesn’t spread. If the exploit targeted a website, consumer information might also be at risk.

It is important to alert all parties to the exploit, as they may need to reset passwords and move personal data.

Implement a BDR strategy as well. If you can rehost essential services as an enterprise, it’s recommended to do so. You can additionally shield valuable data via third-party services. Ultimately, you are looking to contain the problem until a fix is released. Generally, fixes are released shortly, but only upon discovery of the vulnerability.

In these scenarios, remaining proactive is the best defense. Downloading suspicious programs, responding to unusual emails, or clicking links to unknown domains are vectors malicious attackers use for spreading their zero-day exploit.

As with any safe practice, it’s best to air on the side of caution. Identifying strange behavior in a program or system is another method to identify infected systems.

Zero-day vulnerabilities are an inherent danger to the cybersecurity world. Even the tiniest crack can lead to dangerous exploits, so it’s essential to identify unusual behavior in potentially compromised systems.

If you’d like to learn more about zero-day vulnerabilities or have additional questions about managed cybersecurity services, you can read more at our security blog. In the face of cyber dangers, the best protection is knowledge.


About the author

CyberDefenses Inc.