Red teaming: realistic security testing through simulated attacks

In a networked economy, cybersecurity is one of the central challenges for organisations of every size. While classic security checks such as vulnerability scans and penetration tests deliver valuable insights, their significance is often limited. Red teaming goes a decisive step further: it simulates realistic, multi-stage attacks in order to assess the actual resilience of an organisation holistically.

What is red teaming?

Red teaming is an offensive security methodology in which a specialised team, the red team, takes on the role of a real attacker and attempts to overcome an organisation’s defences with every available means. Unlike a conventional penetration test, the red team does not limit itself to individual systems or applications but attacks the entire organisation: networks, applications, physical access and, above all, the human factor.

The term originally comes from the military. As early as the Cold War, armed forces used so-called red teams to examine their own strategies and defensive positions through the eyes of the adversary. The basic idea was simple and effective: whoever knows their own weaknesses before the enemy exploits them has a decisive advantage. This philosophy has been adopted and developed further by the cybersecurity industry over the past decades.

Red teaming vs. penetration test: what is the difference?

The distinction between red teaming and penetration testing is essential, but in practice it is often blurred. Both methods aim to uncover weaknesses, yet they differ fundamentally in approach, scope and significance.

A penetration test is usually clearly limited: a defined scope (e.g. a web application, a network segment), a fixed time frame and an agreed set of rules. The pentester systematically searches for technical vulnerabilities and documents them. The result is a prioritised list of vulnerabilities with recommendations for remediation.

A red team engagement, on the other hand, pursues a concrete goal, such as access to the domain controller, exfiltration of specific data or physical access to the server room. The path to get there is freely chosen and typically combines several attack vectors: technical exploits, social engineering, physical infiltration and the exploitation of process weaknesses. The red team works covertly and tries to evade detection by the defence team (blue team).

Summary of the differences

• Scope: a pentest is limited to defined systems; red teaming covers the entire organisation
• Goal: a pentest identifies technical vulnerabilities; red teaming tests the responsiveness of the entire defence
• Methodology: a pentest works systematically and openly; red teaming works covertly and opportunistically
• Duration: a pentest typically runs for days to a few weeks; red team engagements extend over weeks to months
• Result: a pentest delivers a list of vulnerabilities; red teaming delivers a realistic picture of actual vulnerability

The phases of a red team engagement

A professional red team engagement follows a structured methodology divided into five core phases. Each phase builds on the results of the previous one and requires specific skills and tools.

Phase 1: planning and scoping

Before the first reconnaissance step, the framework of the engagement is defined. This includes setting the attack objectives, defining the rules of engagement, determining escalation paths and agreeing communication channels for emergencies. What matters in this phase is the coordination between the client and the red team, to ensure that the engagement delivers the desired insight without endangering business operations.

Phase 2: reconnaissance

The reconnaissance phase is the foundation of every successful attack. The red team systematically gathers information about the target organisation, first passively (OSINT), then actively. This includes analysing the IT infrastructure, identifying key people, mapping physical locations and researching publicly accessible information that can be used for the attack.

The decisive insights often emerge in this phase: a LinkedIn profile reveals the technologies in use, a job advertisement exposes security gaps in staffing, a photo on the company website shows the model of the access control system.

Phase 3: initial access

Based on the reconnaissance results, the red team plans the initial access. This can happen via various vectors: targeted phishing campaigns, exploitation of technical vulnerabilities in exposed systems, physical infiltration or social engineering by phone. In practice, experienced red teams often combine several vectors to maximise the probability of success and minimise the probability of detection.

Phase 4: escalation and lateral movement

After initial access, the phase of privilege escalation and lateral movement in the network begins. The red team attempts to take over further systems from a compromised system, extend permissions and gradually approach the defined goal. This phase tests in particular the blue team’s ability to detect and respond to suspicious activity.

This is often where the biggest discrepancy between the assumed and the actual security level shows: even organisations with mature perimeter defences frequently have inadequate internal segmentation and monitoring capabilities.

Phase 5: reporting and follow-up

Reporting is probably the most important phase of a red team engagement. A professional report documents not only the weaknesses found and the successful attack paths, but above all provides a strategic assessment of defensive capability. The report addresses different audiences: a management summary for executive leadership, a detailed technical analysis for the security team and concrete, prioritised recommendations for operational implementation.

The value of a red team engagement lies not in the number of weaknesses found, but in the quality of the improvements derived from them.

When is red teaming worthwhile?

Red teaming is not the right measure for every organisation or at every point in time. It presupposes a certain level of security maturity. Organisations that have not yet implemented basic security measures generally benefit more from a structured penetration test or a security assessment.

Red teaming delivers its greatest value in organisations that already have an established security infrastructure and want to know whether it actually holds up when it counts. Typical triggers for a red team engagement are:

• Validation of existing security measures after major investments
• Preparation for regulatory requirements (e.g. DORA, TIBER-EU)
• Assessment of the responsiveness of the internal security team
• The wish for a realistic picture beyond compliance checklists
• Raising executive awareness of real threat scenarios

Best practices for a successful engagement

From our many years of experience at HRC we have identified a number of best practices that significantly influence the success of a red team engagement:

• Clear objectives: define before the engagement what you want to learn, not just what you want to test. The question determines the value of the results.
• Realistic scenarios: the simulated attacks should be based on the actual threat situation. A red team working with unrealistic resources delivers distorted results.
• Inclusion of all vectors: the strongest firewall is useless if the attacker comes in through the back door. Effective red teaming considers technical, physical and human attack vectors equally.
• Constructive follow-up: the results of a red team engagement should not be used to assign blame. A constructive error culture is essential so that employees can learn from the results.
• Continuity: a one-off red team engagement provides a snapshot. Regular engagements make it possible to measure progress and take new attack techniques into account.

The role of the human factor

In our experience, the human factor is the decisive success factor, for attackers and defenders alike. A red team engagement regularly reveals that it is not technology but processes and human behaviour that represent the most critical weaknesses.

An employee who holds a door open. A helpdesk that resets a password without verifying identity. A developer who leaves credentials in a public repository. These weaknesses do not show up in any vulnerability scan, but they are the entry points real attackers use most often.

The best defence is not the strongest wall, but a team that recognises the attacker before they reach the wall.

Conclusion: rehearse the emergency before it happens

Red teaming is not an exercise for the IT department; it is a strategic instrument for the entire organisation. It delivers an unvarnished, realistic picture of actual vulnerability and makes visible what compliance reports and security audits cannot show: how does the organisation behave when a motivated, competent attacker pulls out all the stops?

For organisations that take their security maturity seriously, red teaming is not an optional luxury but a necessity. It closes the dangerous gap between supposed protection and actual vulnerability.