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Internal network pentesting: 5 common mistakes that lead to total compromise

2 minutes
min read
May 23, 2025

Internal network pentesting is essential for identifying weaknesses within an organization’s internal infrastructure. However, even well-planned pentests can fall short if common mistakes are not addressed. Weak segmentation, outdated software, and poor credential hygiene are just a few errors that can lead to a full network compromise. To help security teams enhance their approach, we’re breaking down the top five mistakes that could put your internal network at risk—keep reading to find out how to avoid them.

Poor network segmentation

One of the most common mistakes identified during internal network penetration testing is inadequate segmentation. Organizations often fail to isolate sensitive areas of their network from less critical systems. This lack of segmentation makes it easier for attackers to move laterally once they gain initial access.

How to fix it:

  • Implement network segmentation to isolate sensitive data and systems.
  • Use VLANs and firewall rules to control traffic between segments.
  • Regularly test segmentation controls during pentesting.

Outdated software and unpatched systems

Relying on outdated or unpatched software is a critical vulnerability that attackers exploit. Internal network pentests frequently uncover legacy systems with known vulnerabilities, making the entire network susceptible to attacks.

How to fix it:

  • Regularly update software and operating systems.
  • Implement a patch management policy that prioritizes critical updates.
  • Use automated tools to monitor and detect outdated versions.

Weak credential hygiene

Credentials are often the weakest link in internal networks. Poor practices such as default passwords, weak password policies, or credentials stored in plaintext can lead to quick compromises during pentests.

How to fix it:

  • Enforce strong password policies and multi-factor authentication (MFA).
  • Audit credentials stored on systems and remove or secure weak entries.
  • Train employees on password best practices.

Inadequate logging and monitoring

Lack of visibility is a common issue revealed during network penetration testing. Without adequate logging and monitoring, attacks can go undetected for extended periods, allowing intruders to maintain persistence.

How to fix it:

  • Set up centralized logging to collect and correlate network activity.
  • Implement real-time monitoring with alert thresholds for unusual behavior.
  • Regularly review logs to identify potential intrusions.

Unsecured internal services

Many organizations overlook internal services, leaving them exposed to internal threats. Services like database servers, file shares, and internal APIs often lack sufficient access controls.

How to fix it:

  • Restrict internal service access to authorized users only.
  • Perform regular internal audits to discover exposed services.
  • Harden internal systems by applying the principle of least privilege.

Improving internal network security requires identifying and addressing these common pitfalls. By conducting thorough internal network pentesting and implementing robust security measures, organizations can reduce the risk of a complete network compromise. Remember, proactively fixing these issues is far more effective than reacting to a breach after it occurs.

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