The Cost of Detection Delays: Lessons from Assumed Breach Simulations

For most organizations today, the question isn’t whether they will be breached, but how quickly they can identify and contain it. Preventive controls remain critical, but they are not foolproof in an era where phishing, insider threats, and credential theft continue to bypass even the strongest defenses. This is why many CISOs are embracing Assumed Breach Penetration Testing (ABPT): a methodology that focuses on what happens after attackers are already inside.

The most consistent takeaway from these tests is stark: detection delays are the true cost driver of modern cyber incidents. The longer adversaries dwell undetected, the more business, regulatory, and reputational damage accumulates.

The Importance of Detection Speed

Modern security leaders recognize that threat actors exploit one key asymmetry: time. A threat actor only needs one gap to gain a foothold, but defenders must monitor continuously and react instantly.

• Industry Benchmarks: Reports from Mandiant and IBM X-Force indicate that average dwell times for sophisticated attacks range from 100 to 200 days.

• Business Translation: Each additional day undetected increases the likelihood of data theft, ransomware deployment, and reputational damage.

• Executive Lens: For CISOs reporting to boards, “time to detect” is becoming as important a KPI as revenue protection or compliance status.

Top Takeaways from Assumed Breach Simulations

Via ABPT, ethical hackers assume a threat actor has obtained access to an internal endpoint, whether via phishing, a malicious insider, or compromised remote access. They then simulate the next moves they would take to escalate privileges and move laterally.

What does this showcase to organizations?

1. Lateral Movement is Key

Once a foothold is established, Red Teamers demonstrate how quickly attackers can escalate privileges. Misconfigured Active Directory, weak segmentation, or shared credentials often enable a domain-wide compromise in hours.

Solution: Invest in identity governance, network segmentation, and behavioral monitoring. Don’t stop at asking if SOC spotted the initial intrusion; instead, ask how quickly they noticed privilege escalation attempts.

2. Alert Fatigue Obscures Real Threats

In many assumed breach exercises, the SOC generates alerts but fails to act. Analysts drown in 10,000+ daily events, most of them noise. Red Teams exploit this by mimicking benign activity patterns.

Solution: Prioritize detection engineering. Fewer, higher-confidence alerts will enable your internal security team to respond faster.

3. Exfiltration Is Silent, Not Explosive

Contrary to the “data dump” narrative, most attackers exfiltrate incrementally, over encrypted channels, blending into legitimate traffic. Assumed breach tests often highlight that small, steady leaks go unnoticed for months.

Solution: Implement Data Loss Prevention (DLP) at egress points, and baseline outbound traffic flows.

4. Response Plans Break Down at Escalation

A recurring finding is not detection, but escalation. Analysts see suspicious activity, yet internal bureaucracy or hesitation delays incident classification. In some cases, days pass before leadership is notified.

Solution: Rehearse escalation paths quarterly. Make sure SOC analysts have empowered authority to trigger IR playbooks without waiting for sign-off.

Real-World Lessons: Breach Case Studies

• Target (2013): The breach was detected by security tools but ignored by analysts, allowing attackers to dwell for weeks. The cost: $162 million after insurance.

• Equifax (2017): Vulnerabilities went unpatched, but worse, suspicious traffic went undetected for 76 days, enabling massive data exfiltration.

• Colonial Pipeline (2021): Detection was delayed, and by the time leadership responded, ransomware had disrupted fuel supplies across the U.S.

The thread connecting each case study? Tools didn’t fail; detection speed and human escalation failed.

The Business Cost of Detection Delays

Financial

• Breaches cost an average of $4.45M globally, with delayed detection being the largest multiplier.

• Regulatory fines (GDPR, HIPAA, PCI DSS) escalate when “undue delay” in discovery is proven.

Operational

• Prolonged dwell time increases the chance of business disruption, ransomware deployment, and system downtime.

• Supply chain partners may suspend integrations if they believe the compromise is uncontrolled.

Reputational

• Client and customer trust is damaged when reports reveal that threat actors have had months of unchecked access.

• Brand recovery timelines often outlast the technical cleanup.

CISO Action Plan: Shrinking the Detection Window

• Run Assumed Breach Testing Annually or Semi-Annually: Treat it as a fire drill for your SOC, validating whether adversary behaviors trigger meaningful alerts.

• Measure and Report MTTD (Mean Time to Detect): Include it in board-level dashboards alongside revenue protection and compliance posture.

• Invest in Threat Hunting Teams: Don’t wait for alerts—hunt proactively for anomalies tied to known adversary TTPs.

• Strengthen SOC-IR Integration: Ensure incident response plans are linked directly to SOC detection criteria.

Conclusion

Assumed breach simulations continue to prove that the greatest vulnerability in enterprise defense isn’t always a missing patch or misconfigured firewall: instead, it's the cost of detection delays.

For CISOs, the message is clear: investing in faster detection, tuned alerts, proactive threat hunting, and streamlined escalation is the most cost-effective path to reducing breach impact. In the language of the board, that means protecting revenue, reputation, and regulatory standing.