In cyber security, two terms are often used interchangeably but mean very different things: penetration testing and red teaming. Both involve authorised simulations of cyber attacks designed to uncover weaknesses, yet they differ in scope, intent, and the insights they provide.  A penetration test reveals where defences can be strengthened, while a red team exercise demonstrates how those defences perform under pressure. Understanding those differences helps organisations choose the right approach, invest resources effectively, and strengthen overall resilience.

In this article, we’ll define each approach, explain how they’re conducted, and outline when to choose one over the other – helping you build a more complete view of your organisation’s cyber strategy.

What is penetration testing in cyber security?

Penetration testing (or pentesting) is a controlled and authorised simulation of cyber attacks designed to identify and validate security weaknesses before they can be exploited by malicious actors. It provides organisations with clear visibility into how secure their systems, applications, and networks truly are.

During a pen test, security consultants use a combination of automated tools and manual techniques to identify and validate weaknesses such as misconfigurations, outdated software, or insecure coding practices. The goal is to confirm which issues are genuinely exploitable and to demonstrate their potential business impact, helping organisations prioritise remediation effectively.

Pen testing engagements are typically scoped and time-boxed, focusing on specific systems or environments. Depending on the level of access granted, tests can take the form of black box, grey box, or white box assessments – each offering a different balance between realism, depth, and efficiency.

The outcome is a detailed, risk-ranked report outlining confirmed vulnerabilities, their potential consequences, and clear remediation guidance. When delivered by a CREST-accredited provider, a penetration testing service ensures testing is conducted safely, transparently, and with minimal disruption to operations.

To learn more about how these assessments strengthen security and support compliance, explore our pen testing services.

What is red teaming in cyber security?

Red teaming is a realistic, intelligence-led simulation of how an actual attacker might attempt to compromise your organisation. Unlike penetration testing, which focuses on finding specific technical vulnerabilities, red teaming is objective-driven, designed to test how effectively your organisation can detect, respond to, and contain a sophisticated cyberattack.

A red team engagement is typically carried out over a prolonged period of time (weeks or months) and follows the tactics, techniques, and procedures (TTPs) used by real-world adversaries. These may include social engineering, phishing, physical intrusion, and advanced lateral movement within networks. The goal is not to uncover every weakness, but to assess whether your existing defences, security monitoring, and incident response processes can identify and stop a realistic threat before it reaches critical assets.

Each exercise is conducted under strict rules of engagement and agreed objectives. Testing is performed safely, with predefined escalation points and continuous communication between the red team and the client’s management contacts. This ensures that even though attacks are simulated covertly, they do not disrupt business operations or put data at risk.

At the end of a red team engagement, organisations receive a narrative-style report detailing the attack paths taken, the points of detection or evasion, and practical recommendations to strengthen both preventive and detective controls. As CREST guidance suggests, the true value of a red team exercise lies in understanding how well your organisation performs under pressure and where defensive improvements can have the greatest impact. When performed by experienced consultants, a red teaming engagement offers an accurate measure of real-world resilience, revealing how your systems, people, and processes would respond to a genuine cyber attack.

Penetration testing vs red teaming: Key differences explained

While both approaches simulate real-world attacks, their purpose and scope differ significantly. Penetration testing focuses on identifying and validating specific vulnerabilities within defined systems or applications. It provides clear, actionable insight into where weaknesses exist and how they can be remediated.

Red teaming, by contrast, takes an adversarial perspective. It is not limited to technical flaws but aims to achieve a realistic objective such as accessing critical data or evading detection. Unlike penetration tests, red team exercises are typically conducted without the knowledge of the defensive (blue) team to observe genuine detection and response capability. This approach tests how well an organisation’s defences, people, and processes work together to identify and contain a sophisticated attack. In essence, penetration testing answers the question “Where are our weaknesses?”, while red teaming asks, “Can we detect and stop an attack in progress?” The two complement each other: one strengthens prevention, the other validates detection and response.

When to use penetration testing vs red teaming

Deciding between penetration testing and red teaming depends largely on your organisation’s security maturity, objectives, and the type of assurance you need. While both approaches strengthen resilience, they deliver different forms of value at different stages of a security programme.

Penetration testing is the right choice when the goal is to evaluate technical defences and identify exploitable weaknesses before attackers can. It’s ideal for organisations building or refining their security foundations, those that want to validate patch management, review system hardening, or meet compliance frameworks such as ISO 27001 or PCI DSS. A pen test provides clear, actionable insight into vulnerabilities that could lead to compromise and helps prioritise remediation based on risk.

Red teaming, on the other hand, is designed for mature organisations seeking to test how their defences perform under realistic pressure. Rather than focusing on individual vulnerabilities, a red team exercise evaluates how effectively your people, processes, and technologies detect, respond to, and contain an attack in progress. It’s the most effective way to measure how well your organisation would handle a genuine breach scenario, from initial compromise to incident response and recovery. For many businesses, the most effective strategy combines both. Regular penetration testing ensures that systems remain hardened against known threats, while periodic red teaming validates the organisation’s ability to detect and respond to sophisticated attacks.

How penetration testing and red teaming work together

A mature security programme often begins with regular penetration testing to uncover and remediate technical vulnerabilities. Once a solid defensive baseline is in place, red teaming builds on that foundation by testing how those controls perform under realistic attack conditions. Insights from both exercises reinforce one another, helping to strengthen technology, refine processes, and improve team coordination.

Some organisations take this further with purple teaming – where offensive (red) and defensive (blue) teams work together throughout the exercise. Rather than waiting until the end to review results, defenders observe attacks in real time, fine-tuning detection rules, alerts, and response processes as they go. This cooperative approach accelerates learning, turning every test into a live training exercise that improves long-term capability. Ultimately, penetration testing and red teaming are most powerful when treated not as one-off engagements but as complementary, recurring components of a mature security lifecycle. By combining proactive vulnerability discovery with realistic attack simulation, organisations can move beyond compliance-focused testing and achieve continuous assurance that strengthens both their defences and their confidence in facing today’s evolving threats.

Penetration testing and red teaming FAQs

How Sentrium can help

Penetration testing and red teaming serve different but equally important purposes within a modern security strategy. Penetration testing strengthens prevention by identifying and fixing vulnerabilities before attackers can exploit them. Red teaming, meanwhile, validates how your organisation performs under real-world pressure by testing detection, response, and teamwork when it matters most.

Used together, they provide complete visibility. Pen testing helps you build secure foundations, while red teaming demonstrates how well those defences hold up against a determined adversary. The result is not just compliance but genuine confidence in your ability to withstand today’s evolving threats.

At Sentrium Security, our CREST-accredited consultants deliver penetration testing and red teaming engagements with precision and transparency. We help organisations measure, strengthen, and demonstrate their resilience in the face of evolving threats. To learn more about how our pen testing services can help protect your organisation, get in touch with our team today.