What Is Penetration Testing?
Penetration testing, often called pentesting, is a simulated cyberattack on a computer system, network, or application to identify vulnerabilities. This process involves ethical hackers attempting to breach security defenses using various techniques and tools. The objective is to detect weaknesses before malicious entities can exploit them.
Organizations employ pentesters to ensure that their defenses can withstand real-world cyber threats. It is part of a proactive cybersecurity strategy. By conducting regular pentesting, organizations can improve their security measures, adapting to new threat landscapes and reinforcing their defenses against evolving cyber threats.
Another aspect of penetration testing is providing organizations with insights into their security posture. This involves generating reports detailing identified vulnerabilities, risk levels, and recommended remediation steps. Pentesting helps in finding existing vulnerabilities and assesses the effectiveness of security measures currently in place.
Types of Penetration Testing
Pentesting includes different techniques aimed at assessing various facets of an organization’s security framework.
External Testing
External penetration testing focuses on identifying and exploiting vulnerabilities in an organization’s internet-facing assets. These may include web servers, mail servers, VPN gateways, and domain name system (DNS) services. The test simulates an attacker with no internal access, replicating threats from hackers operating over the internet.
Testers begin with reconnaissance, mapping out the target's digital footprint using tools to identify open ports, services, and software versions. They then exploit known vulnerabilities, weak configurations, or mismanaged services. Findings from external tests help prioritize patching and improve firewall configurations, intrusion detection systems, and endpoint defenses.
Internal Testing
Internal testing simulates attacks from within the organization’s network perimeter. It reflects scenarios such as a disgruntled employee, a compromised internal account, or a malicious actor who has breached external defenses. The tester typically has some level of access, like a standard user or guest, and attempts to escalate privileges or access sensitive data.
This type of testing reveals the damage an insider or internal breach could cause. It evaluates internal controls, such as segmentation between departments, restrictions on access to sensitive systems, and logging of suspicious behavior. Internal pentests often uncover overlooked weaknesses, such as misconfigured user permissions, excessive trust between systems, or lack of monitoring.
Web Application Testing
Web application testing has a more limited scope than traditional penetration testing. It examines the security of software systems accessible through web browsers. This includes online banking platforms, e-commerce sites, and internal web portals. The test focuses on vulnerabilities defined in the OWASP Top 10, such as SQL injection, cross-site scripting (XSS), cross-site request forgery (CSRF), and broken authentication.
Testers use a mix of automated scanning and manual testing to explore how input is handled, how sessions are managed, and whether data is properly protected. They simulate attacker behavior to see if unauthorized actions can be performed, such as accessing another user's account or bypassing business logic.
Learn more in our detailed guide to web application penetration testing.
Wireless Testing
Wireless testing targets the security of wireless networks and devices, including corporate Wi-Fi, employee laptops, mobile devices, and internet of things (IoT) equipment. It evaluates access controls, encryption protocols (like WPA2 or WPA3), and network segmentation.
Testers attempt to intercept traffic, break encryption, create rogue access points, or impersonate legitimate devices. They also assess how well the network defends against unauthorized connections and data leakage.
Social Engineering Tests
Social engineering tests explore the human element of security by attempting to deceive or manipulate individuals into revealing sensitive information or performing unsafe actions. Common methods include phishing emails, phone pretexting, baiting with infected USB drives, or impersonation during in-person interactions.
These tests measure how well employees recognize and respond to manipulation attempts. They often reveal gaps in training, poor security awareness, or lack of verification procedures.
Physical Penetration Testing
Physical penetration testing assesses the effectiveness of physical security controls. Testers attempt to bypass locks, security guards, and surveillance systems to enter restricted areas or access sensitive equipment like servers or network switches.
Scenarios might involve entering into a facility using fake badges, accessing offices after hours, or planting unauthorized devices. This testing helps evaluate real-world vulnerabilities in physical access controls and how well staff enforce security protocols.
Penetration Testing vs. Red Teaming
While penetration testing and red teaming both evaluate an organization’s security, they differ in scope, objectives, and methodology.
Penetration testing is goal-oriented and scoped to identify and exploit known vulnerabilities in systems, applications, or network segments. It is often time-boxed and focused on breadth over stealth. Pentesters usually operate with some degree of transparency and communicate findings promptly.
Red teaming simulates a full-scale, multi-vector attack mimicking a real adversary. It emphasizes stealth, persistence, and lateral movement to test detection and response capabilities. Red teams do not restrict themselves to predefined targets—they may combine cyber, physical, and social engineering techniques to achieve objectives, such as data exfiltration or domain compromise, often without the defenders’ knowledge.
Phases of a Successful Pen Test
Penetration testing is structured into several phases to methodically uncover and assess vulnerabilities.
1. Scoping
Scoping defines the rules, objectives, and boundaries of a penetration test. This phase ensures alignment between the testing team and the organization on what will be tested, how, and to what extent. It includes identifying in-scope assets such as IP addresses, applications, and facilities, and specifying exclusions to prevent unintended disruptions.
Testers gather technical and business context to understand the environment and identify systems that could impact the organization’s operations. Legal and compliance considerations are addressed, and permissions are documented to authorize testing activities. A well-defined scope prevents ambiguity, limits legal risk, and ensures that the test delivers useful, targeted results.
2. Reconnaissance
Reconnaissance, or information gathering, involves collecting as much data as possible about the target systems, networks, and personnel. This phase helps testers map the attack surface and plan their approach by identifying potential weak points.
There are two types of reconnaissance: passive and active. Passive reconnaissance involves indirect methods like analyzing public data, WHOIS records, DNS information, and employee social media profiles. Active reconnaissance engages with the target directly—ping sweeps, port scanning, or service enumeration—to gather technical information. The goal is to compile a detailed profile of the target to inform the scanning and exploitation phases.
3. Scanning and Vulnerability Identification
In this phase, testers perform detailed scans of the target environment using tools like Nmap, Nessus, or Burp Suite. The objective is to identify open ports, active services, system banners, and software versions. Testers analyze this data to detect known vulnerabilities and misconfigurations.
Scanning is often automated, but manual validation is critical to eliminate false positives. Vulnerability databases, such as CVE and NVD, help map discovered services to potential weaknesses. This step builds a prioritized list of exploitable targets, guiding the next phase of attack simulation.
Learn more in our detailed guide to vulnerability assessment.
4. Exploitation and Privilege Escalation
Once vulnerabilities are identified, testers attempt to exploit them to gain unauthorized access. Exploits may target web applications, network services, or system misconfigurations. This phase confirms the real-world risk posed by the vulnerabilities, distinguishing theoretical risks from practical ones.
After initial access, testers try to escalate privileges to move from limited user roles to administrative or root-level access. This is achieved by exploiting local flaws, such as weak permissions, unpatched kernel vulnerabilities, or credential reuse. The goal is to demonstrate the impact of a breach—whether data can be exfiltrated, systems can be controlled, or further internal movement is possible.
5. Post-Exploitation and Reporting
Post-exploitation involves maintaining access, assessing the value of compromised assets, and evaluating lateral movement opportunities. Testers explore the extent of control they can establish, such as accessing databases, emails, or internal tools. They also check if activities were logged or detected, giving insights into the organization’s monitoring and response capabilities.
Finally, the results are compiled into a detailed report. This includes exploited vulnerabilities, attack paths, risk levels, and recommendations for remediation. Reports often separate technical findings from executive summaries, enabling both technical teams and decision-makers to take informed actions.
Tips from the Expert
Dima Potekhin
CTO and Co-Founder
Dima Potekhin, CTO and Co-Founder of CyCognito, is an expert in mass-scale data analysis and security. He is an autodidact who has been coding since the age of nine and holds four patents that include processes for large content delivery networks (CDNs) and internet-scale infrastructure.
In my experience, here are tips that can help you better strengthen your penetration testing program beyond what’s already covered:
- Perform threat modeling before the test begins: Align the pentest with realistic threat scenarios based on adversary TTPs (tactics, techniques, and procedures) targeting the industry. Use frameworks like MITRE ATT&CK to define attacker profiles and ensure testing simulates the most relevant threats to the organization.
- Use “assumed breach” scenarios in internal tests: Go beyond initial access—start internal tests with assumed access (e.g., a compromised workstation or domain user) and focus efforts on lateral movement, privilege escalation, and data exfiltration. This gives insight into actual blast radius if external defenses fail.
- Test cloud misconfigurations with provider-specific tools: Don’t rely solely on generic pentest tools—use CSP-specific tools (like Prowler for AWS and ScoutSuite for Azure/GCP) to detect permission flaws, overly permissive IAM roles, or insecure storage buckets. Cloud misconfigurations are often missed in traditional tests.
- Apply evasion techniques to assess detection capabilities: Test the blue team by using payload obfuscation, encoding, and C2 (command-and-control) traffic mimicry. Evaluate how well EDR/XDR platforms and SIEM rules detect obfuscated exploits, PowerShell abuse, or living-off-the-land binaries (LOLBins).
- Correlate test results with business impact mapping: Don’t just list vulnerabilities—map each exploited path to actual business assets (e.g., revenue systems, PII databases). This prioritizes remediation based on what matters most and helps justify security investment to leadership.
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