Penetration testing and vulnerability assessment are distinct but complementary cybersecurity practices used to identify and address security weaknesses in an organization's systems. A comprehensive security strategy, often called VAPT, combines both for a robust and proactive approach to defense. 

Vulnerability assessment (VA)

A vulnerability assessment is a proactive, systematic process that uses automated tools to scan and identify security weaknesses in an IT infrastructure, including networks, systems, applications, and APIs. 

Purpose: The main goal is to get a broad overview of an organization's security posture by identifying known vulnerabilities, assigning them a severity rating, and providing recommendations for remediation. 

Methodology:

• Asset discovery: Identify and catalog all IT assets within a defined scope, including network devices, servers, applications, and databases.
• Vulnerability scanning: Use automated scanners (e.g., Nessus, OpenVAS, Qualys) to check for thousands of known vulnerabilities, such as misconfigured settings, unpatched software, or weak passwords.
• Prioritization: Analyze the scan results to remove false positives and prioritize vulnerabilities based on their severity and potential business impact.
• Reporting: Generate a detailed report listing all identified vulnerabilities, their severity, potential impact, and recommended remediation steps. 

Penetration testing (PT)

A penetration test, or "pen test," is a controlled, simulated cyberattack conducted by ethical hackers. The testers actively exploit the vulnerabilities identified during a VA to determine the real-world risk and measure the potential damage of a successful attack. 

Purpose: To demonstrate how vulnerabilities can be chained together to compromise a system and assess how far a real-world attacker could penetrate the network. 

Methodology (based on PTES):

• Planning and reconnaissance: Define the scope of the test and gather intelligence on the target system using both passive (OSINT) and active scanning methods.
• Scanning and enumeration: Conduct in-depth scans to discover services, open ports, and potential entry points.
• Gaining access: Attempt to exploit identified vulnerabilities to gain initial access to the system.
• Maintaining access and privilege escalation: Once initial access is gained, the tester tries to escalate privileges and move laterally through the network to gain deeper access.
• Covering tracks and cleanup: The tester removes all tools and scripts and restores the system to its original state to avoid leaving any vulnerabilities or backdoors.

Reporting: Provide a comprehensive report detailing the entire attack path, the specific vulnerabilities exploited, the business impact, and strategic recommendations for mitigation