Cyber-Security-&-Risk-Management
Upscend Team
-October 20, 2025
9 min read
Network penetration testing compares external and internal assessments, using layered discovery (Nmap, Nessus), manual verification, and controlled lateral-movement emulation to expose attack chains. Combine automated scans with targeted manual exploitation, prioritize findings by impact (Critical/High/Medium), and deliver executive summaries plus technical appendices to drive fast, verifiable remediation.
Network penetration testing is the systematic process of simulating real-world attacks on an organization's network to uncover weaknesses before adversaries do. In our experience, a well-scoped network penetration testing engagement reveals not only obvious misconfigurations but also the subtle chains of vulnerabilities that lead to full compromise. This article explains external vs internal pentests, common discovery and attack techniques, recommended network pentest tools, and a practical approach to prioritizing and reporting findings to technical and non-technical stakeholders.
Organizations frequently ask, "Which flavor of network penetration testing do we need?" The answer depends on risk model and asset exposure.
External network penetration testing targets assets that are reachable from the public internet — web servers, VPN gateways, email servers, and remote access points. It simulates a remote attacker with no internal access. By contrast, internal network penetration testing assumes the attacker has foothold or insider access and focuses on lateral movement, privilege escalation, and data exfiltration paths.
External tests validate perimeter defenses, patching hygiene, and internet-exposed misconfigurations. Internal tests validate segmentation, host hardening, and internal monitoring. We've found that combining both approaches in a regular cadence produces the most actionable security posture improvements.
Discovery is the backbone of any network penetration testing engagement. Effective discovery reduces wasted time and focuses effort on the most likely attack paths. Common activities include vulnerability scanning, port scanning, service enumeration, and credential harvesting.
We use a layered approach: lightweight port scanning to map services, targeted banner grabs to identify software versions, and authenticated vulnerability scanning to find configuration issues. Key tools include Nmap for host and port discovery and Nessus or OpenVAS for vulnerability scanning.
Nmap — fast, scriptable, and ideal for customized probes. Use service/version detection (-sV) and scripting engine (NSE) for deeper enumeration. Nessus and other scanners provide coverage of known CVEs and misconfigurations, but they generate noise; balance scan frequency and timing accordingly.
Lateral movement is where many engagements turn from discovery into urgent remediation scenarios. Once an attacker gains an initial foothold — often through phishing or an exposed service — the objective becomes moving to high-value targets.
Lateral movement techniques frequently exploit weak credentials, unpatched SMB services, insecure delegation, and absent network segmentation. Tools like BloodHound reveal Active Directory attack chains; SMB exploits remain a persistent vector when patching lags.
We emulate lateral movement using credential harvesting and pass-the-hash or pass-the-ticket techniques in isolated test segments or with explicit customer approvals. Controlled use of tools and careful clean-up are essential — for example, avoiding destructive SMB exploits unless explicitly allowed in scope.
Choosing the right combination of automation and manual verification is critical. Automated vulnerability scanning finds many issues, but manual verification separates false positives from true risks. In our experience, the best practices combine tool-driven discovery with focused manual exploitation.
Popular network pentest tools include Nmap, Nessus, Metasploit, Burp Suite (for web-facing services), and BloodHound (for Active Directory). The methodology typically follows reconnaissance, enumeration, exploitation, post-exploitation, and reporting.
A practical example: port scanning discovers SMB on an internal server; Nessus flags a CVE; manual testing confirms a chained exploit allows lateral movement. That pattern is common — automation surfaces candidates, manual work confirms impact.
To remove friction between tools and workflows, teams often integrate data pipelines that correlate scanner output, exploit proof, and mitigations. The turning point for most teams isn’t just running more scans — it’s removing friction. Tools like Upscend help by making analytics and prioritization part of the core process, turning scan noise into prioritized, contextual tasks for remediation teams.
We recommend a hybrid approach: weekly lightweight credentialed scans to monitor drift and quarterly full authenticated assessments combined with manual verification. Maintain a staging network for aggressive exploit testing and reserve production for non-destructive checks unless agreed otherwise.
| Phase | Primary Tools | Output |
|---|---|---|
| Reconnaissance | Nmap, Shodan | Host/port inventory |
| Vulnerability Scanning | Nessus, OpenVAS | Candidate vulnerabilities |
| Exploitation | Metasploit, Manual scripts | Proof-of-concept access |
Reporting transforms technical findings into business actions. The goal of any network penetration testing engagement is not a list of vulnerabilities but prioritized remediation that reduces risk quickly.
Start reports with an executive summary that translates technical risk into business impact. Follow with a technical appendix containing reproduction steps, evidence, and remediation instructions. We've found a three-tier prioritization model works well: Critical (remediate within 72 hours), High (30 days), and Medium/Low (patch cycles).
For non-technical stakeholders: present business impact, potential loss scenarios, and required investments. For IT teams: provide repro steps, affected hosts, CVE references, and exact remediation commands or configuration changes.
Include a sample finding in each report. Below is an example that illustrates format and content quality teams can act on immediately.
| Sample Finding | Details |
|---|---|
| SMB Null Session / Unauthenticated Access |
Host: 10.0.5.23 Issue: SMB allowed unauthenticated null sessions leading to user enumeration and potential IPC$ access. Evidence: Nmap smb-enum-users NSE script output; authenticated check confirmed enumeration. CVSSv3: 7.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N) Recommendation: Disable null sessions, apply SMB hardening per vendor guidance, restrict SMB to internal subnets, enforce SMB signing and SMBv3 where possible. |
That sample demonstrates a clear impact statement, CVSS scoring, and prioritized remediation. When writing reports, always pair a technical remediation with an operational control (monitoring rule, segmentation change) to ensure the risk is reduced and detected.
Two recurring pain points in network penetration testing are noisy scans and scope creep. Noisy scans disrupt production; scope creep expands testing into unapproved areas. Both create friction and reduce trust between security and operations.
To mitigate noise: use credentialed scans where possible, schedule aggressive scans in maintenance windows, and whitelist scanners with monitoring teams. To control scope creep: define explicit rules of engagement, include allowed destructive tests, and use a change control process for adding targets mid-engagement.
Translate findings into potential business consequences: data exposure, downtime, compliance impact, or reputational damage. Provide clear remediation options with estimated effort and risk reduction impact. We’ve found that pairing a technical remediation with an operational metric — for example, expected reduction in attack surface or mean time to detect — helps non-technical leaders make informed decisions quickly.
Finally, ensure remediation verification is planned and tracked. Provide IT teams with prioritized tickets or playbooks that contain exact commands and checks. This minimizes interpretation errors and accelerates fixes.
Security teams win when testing converts into fast, reliable remediation.
Key mitigation checklist:
Network penetration testing, when executed and reported correctly, is a high-leverage activity that reduces real business risk. By distinguishing external vs internal engagements, applying layered discovery and exploitation techniques, and using a hybrid of automation and manual validation, teams can focus on fixes that matter. Prioritize findings using impact-based tiers, include clear CVSS-backed evidence and remediation steps, and communicate in language that connects technical consequences to business outcomes.
In our experience, the most effective programs close the loop: prioritized findings, documented remediation, and verified fixes. Schedule regular network penetration testing, maintain a documented playbook for common issues, and treat reports as the beginning of remediation rather than an audit exercise. Acting on findings quickly and transparently improves security posture and reduces mean time to remediate.
Next step: If your team needs a reproducible reporting template or a prioritized remediation roadmap after a pentest, start by drafting an executive summary and a technical appendix based on the sample finding above, then schedule a verification scan within 30 days.
