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What is a False Negative in Cybersecurity?


What is a false negative in cybersecurity?

In penetration testing, both false negatives and false positives can trigger application security vulnerabilities. But what is it about false negatives that are so potentially hazardous to your organization's cyber health?

Let's explore:

What is a False Negative in Penetration Testing? (And What About False Positives?)

When an automated vulnerability scan provides a wrong result, two types of error are possible: a false negative, which is when the test incorrectly says that nothing was found, and a false positive, which is when the test sends an alert for a vulnerability that does not exist.

Whether you are using a vulnerability scanning tool or another form of vulnerability identification, here are the breakdowns of both types of errors:

  • Type I error (false positive): a result that indicates a vulnerability is present when it is not. This creates noise and results in unnecessary remediation work

  • Type II error (false negative): where a vulnerability is present but is not identified

False negatives are deemed as the more severe type of error due to how they form a false sense of security for both the organization and the cybersecurity team involved.

In the context of application security testing, since the test's end goal is to detect vulnerabilities that your organization has not been made of aware of yet, understanding the idea of false negatives is critical to know when dealing with artificial test environments (which are commonly used for security benchmarking or evaluation.)

For further context, false positives are more significant in real-world security testing scenarios. This is because cybersecurity solutions that don’t have the technology to decide whether some application behavior indicates a vulnerability often err on the side of caution and report everything they find, even if it means many false alarms. This makes results inherently uncertain and impossible to automate security workflows.

The Consequences of False Negatives in Application Security Testing

When a security alert goes undetected, the attacker has a free hand to carry on. Depending on the attacker’s expertise, perseverance, and motivation, this can result in anything from a little nuisance to a full-blown system breach.

Consequences that may occur include, but are not limited to:

  • Data breaches: Data breaches have the potential to result in a significant quantity of negative publicity, harm to the organization’s image in the industry and among its consumers, the creation of legal liabilities, and significant financial penalties from privacy regulators

  • Loss of intellectual property: If infiltration is successful, it may lead to the later loss of trade secrets and other forms of intellectual property. Depending on the industry, this can be disastrous for profit margins and potentially wipe out a company’s former hold on the market leadership position.

  • Ransomware vulnerability: Ransomware is a type of malicious software that, if it successfully penetrates a system, will encrypt all of its data and refuse to decrypt it unless the attacker receives a substantial ransom payment. Attacks using ransomware are notably prevalent in the healthcare field; however, incidents of this can arise in any sector

The Cost of False Negatives in Application Security Testing

It is becoming increasingly challenging in 2023 and beyond for key stakeholders to keep up with the ever-increasing number of cyber warnings, threats, and breaches year over year.

Much of this is attributed to "alert fatigue". Alert fatigue refers to those belonging to an organization becoming desensitized to cybersecurity dangers, which, in turn, results in prolonged reaction times or ignored notifications.

To further exacerbate this problem, IT departments are more likely to suffer from burnout once the stage of alert fatigue has been reached, leading to a higher staff turnover rate and poorer overall performance. The cycle repeats as new employees are brought in with increasing downturns in performance and overall security posture.

Excess alerts, unnecessary notifications, false negatives, and false positives all lead to one end result: alert fatigue.

Recent studies have shown that:

  • Every actionable alarm takes an average of 30 minutes, whereas every false lead takes an average of 32 minutes to investigate

  • Approximately 27% of all notifications are ignored or never investigated by organizations that have between 500-1,499 employees

  • 70% of respondents stated that the emotional stress of IT threat alerts negatively impacted their home life

  • 51% of those surveys reported that the number of cyber alerts they receive is detrimental to their team's performance

  • 55% of organizations are not confident in their ability to both prioritize and respond to cybersecurity threats in 2023

  • IT teams surveyed say that they spend up to 27% of their time on average dealing with either false negatives or false positives

Why Vulnerability Scans Produce False Negatives

In a vulnerability scan, a false negative is a fancy way of saying that your security solution missed a vulnerability.

Why is this so common in 100% automated VAs? Well:

Reason #1: Coverage

Accuracy in the crawling phase of a VA scan is critical. Modern websites often use custom error pages to provide user-friendly error messages, the rewriting of URLs to strengthen search engine optimization, anti-CSRF tokens to bolster security, and authentication to restrict access to protected data.

A less sophisticated scanner may struggle to find all the places it needs to test; as such, if it stumbles on authentication, it might leave whole sections of the application unscanned. 

Reason #2: Security Check Processes

The core of an application security test is the security checks. VA scanners started life as scripts to automate routine tasks during manual penetration testing, but a modern application security solution has to go significantly further. The goal is no longer to speed up manual testing; instead, it is to do the tests automatically with little or no human element.

However, every missed vulnerability is a security risk and every false alarm creates additional work, so an inaccurate scanner can be worse than having no scan done.

Reason #3: Configuration

A VA scanner simulates the actions of threat actors by manipulating user-accessible page elements and other exposed endpoints. Every web application is different, so, in order to conduct this accurately, both extensive setup and technical prowess are required.

Suppose the tool is not advanced enough or the team wielding it does not have the resources to manually set up all the scan parameters. In that case, the scanner might miss many vulnerabilities simply because it’s not testing the right places and in the right way.

How to Avoid False Negatives in Cybersecurity

Designing automated tests that can accurately pinpoint defects in software can be challenging. As scanners run and tests are conducted, false negatives happen when problems aren’t picked up even though there are bugs or vulnerabilities in the application that is being targeted. In the case of a false negative, the test passes when a bug or security vulnerability is present or the functionality is not working as it should be.

The more times testing tools and strategies give false negatives (as well as false positives), the less reliable and less valid the results are. Although both false alerts are a problem, especially when it comes to alert fatigue, a false negative is deemed more damaging because it lets a problem go undetected, creating a false sense of security.

(Why? Because, while a false positive may consume much of a tester’s energy and time, a false negative allows a bug to remain in the software.)

So how can you avoid false negatives in cybersecurity? There's one answer: invest in 95% manual penetration testing.

Rather than automated vulnerability scans, which are not in-depth and do not have the human element to act as a fallback when false negatives or positives occur, 95% manual pentesting takes cybersecurity beyond the checkbox: by incorporating the element of OSCP-minimum certified ethical hackers, organizations like yours are better protected against automated fallacies.


When it comes to what a false negative in cybersecurity is, it's crucial to remember that real-life effectiveness is key in any application security test. The best way to see if a solution is right for your organization is to run it on your actual applications with vendor assistance to make sure the setup is beneficial to your organization's specific needs.

Here at Packetlabs, we are a SOC 2 Type II accredited cybersecurity firm specializing in penetration testing services. To strengthen your security posture, we offer solutions such as penetration testing, adversary simulation, application security and other security assessments.

On top of employing only OSCP-minimum certified ethical hackers, the Packetlabs difference boils down to our 95% manual penetration testing. Instead of outsourcing our work or relying on automated VA scans, we guarantee zero false positives via our in-depth approach and passion for innovation: our security testing methodology is derived from the SANS Pentest Methodology, the MITRE ATT&CK framework for enterprises, and NIST SP800-115 to ensure compliance with the majority of common regulatory requirements. Our comprehensive methodology has been broken up based on which areas can be tested with automation and those which require extensive manual testing.

Alongside recently celebrating our twelfth year in business this year, our 95% manual penetration testing yielded a partnership with the SickKids Foundation, which was another one of our 2023 highlights: the SickKids Foundation is a fundraising organization based in Toronto that supports the Hospital with sick children. With over 1.5 million active donors, the foundation collects and manages sensitive information, which could result in reputational damage and loss of donors if breached.

Download our Buyer's Guide today or contact our team to learn more about how 95% manual pentesting enhances your application security testing by avoiding common hurdles like false negatives.

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