Grey Box PenTesting: The Overlooked Layer in Network Security
Cyberattacks don’t usually begin with sophisticated hacking techniques. Often, they start with something far simpler—stolen credentials. A phishing attack, a leaked database, or even weak internal security controls can provide an attacker with legitimate access to an organization's network.
Once they’re inside, how much damage can they do?
Many security teams focus on external threats—the hackers trying to force their way in. But what happens when attackers don’t need to break in at all? Grey Box Penetration Testing (Grey Box Pentesting) helps answer that question by testing the security of a network from an insider’s perspective—using limited, but valid, user credentials.
The Gaps in Traditional Security Testing
Penetration testing typically falls into two categories:
- Black Box Testing – Simulates an external attacker with no prior knowledge, testing for perimeter vulnerabilities.
- White Box Testing – Grants full access to testers, allowing for an in-depth review of security controls and internal defenses.
Grey Box Pentesting sits in between, mimicking the more common real-world scenario—an attacker with stolen login credentials, but without administrative privileges.
Think of it like securing a corporate office:
- Black Box Pentesting is like watching someone try to pick the locks or force open a door.
- White Box Pentesting is like handing someone the blueprints and security codes, asking them to find vulnerabilities.
- Grey Box Pentesting? That’s like testing what happens when someone walks in with a stolen employee badge.
Many organizations assume that if an attacker only has a standard user’s access, they’re limited in what they can do. But experience tells a different story. Attacks using stolen credentials have surged by 71% year-over-year (Secureframe), proving that adversaries are leveraging this technique more than ever.
What’s at Risk?
- Exposure from Stolen Credentials
Most cyberattacks today start with compromised credentials. Whether through phishing, credential stuffing, or insider threats, attackers gain valid user access. Grey Box Pentesting reveals the actual impact of these breaches, showing what data is exposed and what systems an attacker can access.
- Weak Permissions & Overprivileged Accounts
A standard user shouldn’t have access to critical systems, but misconfigurations happen. Grey Box testing helps identify permission creep, where users accumulate unnecessary access over time.
- Privilege Escalation Paths
An attacker with basic user access often seeks ways to escalate privileges, gaining administrative control. Grey Box Pentesting tests for misconfigurations, weak service accounts, and exploitable vulnerabilities that allow this kind of movement.
How Grey Box Pentesting Works
Unlike traditional vulnerability scans that focus on static security flaws, Grey Box testing simulates an active attack scenario. Here’s what the process looks like:
- Controlled Access
Testers use valid but limited credentials, such as an Active Directory or local user account, mirroring what an attacker might steal.
- Internal Reconnaissance
They navigate the network, mapping out shared drives, user permissions, and application access—just like a real attacker would.
- Lateral Movement & Privilege Escalation
Testers attempt to move across systems, escalating access where possible, and identifying how far a real attacker could go.
- Actionable Security Findings
Instead of listing generic vulnerabilities, Grey Box reports provide real-world attack narratives, detailing how a breach could unfold and offering step-by-step remediation guidance.
Beyond Compliance: Testing for Real-World Threats
Many organizations conduct penetration testing to meet compliance requirements under SOC 2, PCI-DSS, ISO 27001, and other security frameworks. These standards typically require a mix of internal and external assessments to evaluate both perimeter security and risks inside the network.
However, compliance-driven tests often focus on checking the necessary boxes rather than identifying the most realistic attack vectors. Grey Box Pentesting goes a step further by simulating real-world threats where attackers gain access through compromised credentials and attempt to escalate privileges or move laterally within the network.
The Future of Pentesting: Automating Security Assessments
Penetration testing has traditionally been a manual process—time-intensive, expensive, and often performed only once a year. But cyber threats don’t wait for annual security reviews.
Automated pentesting solutions like vPenTest are changing that, providing continuous, scalable, and real-time security assessments that eliminate the gaps left by periodic manual testing.
- Testing More Often, More Efficiently
Instead of a one-and-done assessment, automated pentesting solutions like vPenTest allow companies to run tests as often as needed, identifying new vulnerabilities as they emerge.
- Simulating Real Credential-Based Attacks
Platforms like vPenTest now support Grey Box Pentesting, meaning security teams can automatically test their networks using real credentials to simulate insider threats.
- Cost-Effective Security Testing
Hiring penetration testers for every security update, network change, or new application deployment isn’t feasible for most companies. Automated solutions scale security assessments across the entire organization without requiring additional resources.
- Faster, Actionable Insights
Instead of waiting weeks for a pentest report, automated tools provide instant findings with clear remediation steps, allowing security teams to fix vulnerabilities before they’re exploited.
Are You Testing Your Network Like an Attacker Would?
The reality is that attackers aren’t just brute-forcing their way into systems. They’re using stolen credentials, weak permissions, and misconfigurations to move through networks undetected.
Grey Box Pentesting provides the missing link in security testing, showing exactly how far an attacker could go once inside. And with the rise of automated pentesting solutions like vPenTest, organizations can test continuously, uncover internal weaknesses, and stay ahead of attackers.
With attacks using stolen credentials increasing by 71% year-over-year (Secureframe) and the cost of a data breach reaching $4.88 million (IBM), the question isn't if an attacker will try to exploit your network—it’s whether you’ll find the gaps before they do.
If you’re only testing your perimeter, you’re not testing your real risks. It’s time to test security the way attackers exploit it.
vPenTest’s New Feature: Grey Box Internal Network Pentesting
With vPenTest’s feature, Grey Box Internal Network Pentesting, security teams can now easily and automatically simulate real-world credential-based attacks using Active Directory or local credentials—no complex setup or manual effort required.
This feature helps organizations:
- Identify privilege escalation risks and misconfigurations that could be exploited.
- Uncover excessive permissions that expose sensitive data.
- Run automated, continuous pentests to strengthen security without disrupting operations.
Rather than waiting weeks for a traditional pentest report, vPenTest delivers on-demand network pentests with detailed, actionable reports—helping teams fix exploitable vulnerabilities before the bad guys do. It’s time to move beyond one-time security checks and take a proactive, automated approach to network security.