Network Penetration Testing for Regulated Mid-Market Organizations

SENTRY — Penetration Testing

Network Penetration Testing for Regulated Mid-Market Organizations

Network penetration testing validates whether your perimeter defenses, internal segmentation, and Active Directory controls hold against real attack techniques — and produces the documented evidence your compliance framework requires.

What Network Penetration Testing Examines

Network penetration testing is the foundational security assessment for most organizations. It targets the infrastructure layer — firewalls, routers, switches, VPNs, servers, and services — using the same reconnaissance, exploitation, and lateral-movement techniques documented in the MITRE ATT&CK framework.

A credible network penetration test is not a port scan with a PDF attached. It involves manual exploitation attempts against identified services, authentication attacks against exposed interfaces, configuration analysis of network devices, and — in internal assessments — Active Directory attack-path analysis, credential harvesting, and lateral-movement simulation. Armorstack’s SENTRY team follows PTES and NIST SP 800-115 throughout every engagement.

Most compliance frameworks require both external and internal network penetration testing. External testing assesses what an internet-based attacker can reach and exploit. Internal testing simulates post-breach conditions — what happens when an attacker has already bypassed perimeter controls through phishing, credential theft, or vendor compromise.

Perimeter Assessment

External Network Penetration Testing

External testing begins with passive reconnaissance — OSINT collection, DNS enumeration, certificate transparency analysis, and identification of external-facing IP ranges and services — mirroring how sophisticated attackers profile a target before attempting exploitation.

01

Passive Reconnaissance

OSINT collection on your organization’s internet presence, DNS enumeration, certificate transparency analysis, and mapping of external-facing IP ranges and services.

02

Service Enumeration

Enumeration of open ports and services across external IP ranges, with service-version identification for known-vulnerability mapping.

03

Exploitation Attempts

Manual exploitation attempts against publicly known and zero-day-adjacent vulnerabilities identified in exposed services.

04

Authentication Interface Testing

Credential-based attacks against exposed authentication surfaces — VPN, OWA, RDP, and web administrative portals.

05

Firewall & Egress Analysis

Evaluation of firewall rule adequacy and egress filtering controls against realistic exfiltration paths.

06

Common Findings

Legacy TLS configurations, unauthenticated administrative portals, VPN gateways vulnerable to known CVEs, exposed management interfaces, and DNS misconfigurations enabling zone transfer or subdomain takeover.

External network penetration testing satisfies the external-assessment component of PCI-DSS Requirement 11.4, HIPAA technical evaluation requirements, GLBA Safeguards Rule annual testing obligations, and the external-facing assessment objectives within CMMC-aligned testing programs. See penetration testing for CMMC for how this maps to NIST SP 800-171 controls.

Assumed Breach

Internal Network Penetration Testing

Internal testing begins from an assumed-breach position — a tester with network access at the level of a standard workstation or an authenticated VPN user. This is the realistic starting point for most breach scenarios, because the majority of significant compromises begin with a phishing email or a compromised credential, not a direct firewall bypass. Internal testing evaluates network segmentation controls, lateral-movement opportunities, Active Directory attack paths, trust relationships between systems, credential storage practices, service-account privilege levels, and whether an attacker who gains initial foothold can escalate to domain administrator or reach sensitive data stores.

Active Directory Attack Path Analysis

Active Directory is the primary identity infrastructure for most mid-market Windows environments and the primary target for attackers who have achieved initial access. Internal testing enumerates AD misconfigurations — Kerberoastable service accounts, AS-REP roasting candidates, unconstrained delegation, ACL misuse, and pass-the-hash opportunities — that enable privilege escalation without exploiting software vulnerabilities. These findings are often invisible to vulnerability scanners, which do not model attack chains through identity infrastructure.

Network Segmentation Validation

Segmentation controls are only meaningful if they hold under adversarial conditions. Internal testing validates whether network segments that are supposed to be isolated — PCI cardholder data environments, healthcare clinical networks, OT environments, privileged management networks — are actually inaccessible from standard network positions. Segmentation failures are among the most common and consequential findings in internal assessments.

Methodology

Network Penetration Testing Methodology

Armorstack’s SENTRY network penetration testing follows PTES phases aligned to NIST SP 800-115, Technical Guide to Information Security Testing. Findings are mapped to MITRE ATT&CK tactics and techniques, giving your security team and your compliance documentation a common reference framework.

01

Rules of Engagement

Every engagement includes rules-of-engagement documentation before testing begins, scoping the systems, timing windows, and escalation contacts.

02

Testing Execution

PTES-phased external and/or internal testing executed manually against identified services, interfaces, and identity infrastructure.

03

Critical Finding Escalation

A defined escalation procedure for vulnerabilities requiring immediate remediation — findings are not held for the final report.

04

Reporting & Remediation

A final report with executive-summary and technical-findings sections. Technical findings include CVSS scores, reproduction steps, and specific remediation guidance — not generic recommendations your team cannot act on.

Beyond the Point-in-Time Report

Connecting Network Testing to Continuous Monitoring

A network penetration test tells you the state of your environment on the day of the engagement. The attack paths identified during testing remain relevant until remediation is confirmed — and new paths emerge as your environment changes. Armorstack’s managed detection and response capability monitors your network for exploitation attempts against the same attack vectors identified during testing and provides the continuous visibility layer that point-in-time testing cannot.For organizations that need governance context around network penetration testing findings — risk prioritization, remediation timelines, board reporting — the VERITY risk advisory practice connects technical findings to strategic risk decisions.

For a full picture of how network penetration testing fits within a broader assessment program, see the penetration testing services overview. To understand how this differs from vulnerability scanning, see the pen test vs. vulnerability scan comparison. To scope an engagement, contact the SENTRY team.

FAQ

Frequently Asked Questions

What is the difference between external and internal network penetration testing?
External network penetration testing assesses what an internet-based attacker can reach and exploit from outside your perimeter. Internal network penetration testing simulates post-breach conditions — what an attacker who has already gained network access can do through lateral movement, Active Directory attacks, and privilege escalation. Most compliance frameworks require both.
What does internal network penetration testing include?
Internal network penetration testing includes network segmentation validation, Active Directory attack path analysis (Kerberoasting, ACL abuse, unconstrained delegation), lateral movement simulation, credential harvesting analysis, service account privilege review, and assessment of what data an attacker could reach from a standard workstation-level starting position.
Does network penetration testing satisfy PCI-DSS requirements?
Yes. PCI-DSS v4.0 Requirement 11.4 mandates external and internal network penetration testing at least annually and after significant infrastructure changes. The testing must be performed by a qualified internal resource or third party, and findings must be documented, remediated, and retested.
What methodology does Armorstack use for network penetration testing?
Armorstack’s SENTRY team follows the Penetration Testing Execution Standard (PTES) and NIST SP 800-115. Findings are mapped to MITRE ATT&CK tactics and techniques. Every engagement includes rules of engagement documentation, a critical finding escalation procedure, and a final report with CVSS scores and specific remediation guidance.

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