Recently, there was a report about a zero-day vulnerability being patched for Windows. This was a significant threat that could allow an attacker to gain elevated permissions on compromised devices. The flaw was in the Windows Common Log File System (CLFS).
It was noted as the patch was released that hackers were actively exploiting this zero-day vulnerability, meaning they were using it to breach computers and run malicious code.
You may see this type of story in the news often and wonder, “What exactly is a zero-day vulnerability?” How does it differ from any other type of code flaw that is exploited by hackers?
A zero-day vulnerability is more dangerous for one specific reason, it’s so new when first discovered that software developers haven’t yet had time to develop a fix. These code flaws pose an ongoing threat to cyber security and compliance because they are proliferating and offer a window of opportunity to hackers.
Definition of a Zero-Day Vulnerability
The hallmark of a zero-day vulnerability is that it is so new that the developer has not yet created a fix for it. The term “zero-day” refers to the number of days that the software developer has known about the issue.
Zero-day vulnerabilities are often identified only once the hackers have found them first and exploited them. The malware code that hackers write to take advantage of these code flaws is called a zero-day exploit.
Zero-day exploits come in the form of ransomware, spyware, viruses, and other types of malware code. Once these attacks start happening, cyber security professionals researching the breaches identify how they happened. The developer is then notified of the new zero-day vulnerability.
Once a patch is developed and issued for the flaw, then it’s no longer technically considered “zero-day.” But just because a patch has been issued, doesn’t mean corporate networks are safe. The patch, which usually comes through in the form of a software update, needs to be applied. Until it’s applied the system is still open to an attack on the vulnerability.
In 2021, zero-day exploits increased by 167% to an all-time high.
What Damage Can Be Caused by These Code Flaws?
A zero-day vulnerability can be critical in nature or less critical. All vulnerabilities use a scoring system to grade the severity of damage that could be done if that vulnerability is exploited.
Common Vulnerability Scoring System (CVSS):
- Severity: None
- Low severity
- Medium severity
- High severity
- Critical severity
As you can guess, high and critical severity vulnerabilities are the biggest threats. These are classifications that mean hackers can do things like take over a system or run damaging code by exploiting one or more vulnerabilities.
Types of attacks that can be deployed by exploiting zero-day code flaws include:
- Ransomware
- Spear phishing
- Account takeover
- Trojans
- Worms
- Spyware
- Adware
- Crypto mining
When attacked through a zero-day vulnerability, your organization can suffer from expensive downtime, as well as major costs related to a data breach. For example, if personally identifiable information (PII) is exposed, it can mean both a reputation hit and a compliance penalty.
Vulnerabilities are the key that hackers use to gain access to a system. Zero-day is the worst of these for cybersecurity because when they’re first exploited, there may be no patch to stop them.
But that doesn’t mean you have to be a sitting duck for every zero-day exploit that comes along. Following some best practices and taking a zero-trust cybersecurity approach can help you avoid a zero-day attack.
Best Practices for Avoiding Zero-Day Exploits
Keep Software Updated
It’s critical to get zero-day vulnerability patches installed as soon as they are available. Microsoft has what is called “Patch Tuesday,” which is a release of security patches on the second Tuesday of every month. For highly critical zero-day vulnerabilities, it may also release patches outside this schedule.
Good cybersecurity hygiene dictates applying updates to OS, software, and firmware on a regular basis to ensure that no vital security patches are missed.
Have a Good Vulnerability Management Program
Technology infrastructure involves multiple moving parts, often between hundreds of endpoints and network connections. You can prevent a zero-day exploit from wreaking havoc in your system by doing a regular scan for any vulnerabilities and applying vulnerability management.
This means that you keep on top of potential threats and have a process in place to classify and address them. This keeps you from getting surprised by a hidden system vulnerability that you didn’t realize was there until it’s too late.
Limit Application Permissions With Safelisting & Ringfencing
One of the ways to reduce risk when a system has a zero-day vulnerability for which no patch has yet been released is to restrict what applications can do. Zero-day exploits often take advantage of the connection between applications, injecting code that sends malicious commands to system resources.
Safelisting restricts the applications that can run in your system by adding them to a “safe list.” Any code trying to run that is not included is stopped. Ringfencing is a companion cybersecurity service that regulates what applications can do and how they can interact with each other.
Improve Your Ability to Detect System Vulnerabilities
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