🛡️ CISO Playbook • Incident Response

      CyberDudeBivash Exclusive: A CISO’s Playbook for Validating and Escalating Suspected Zero-Days    

By CyberDudeBivash • October 03, 2025 • Strategic Guide

 cyberdudebivash.com |       cyberbivash.blogspot.com 

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Disclosure: This is a strategic guide for security leaders. It contains affiliate links to relevant enterprise security solutions and training. Your support helps fund our independent research.

 IR Playbook: Table of Contents 

1. Chapter 1: The ‘Unknown Unknown’ — The Challenge of a Suspected Zero-Day
2. Chapter 2: Phase 1 — Triage & Containment (The First 30 Minutes)
3. Chapter 3: Phase 2 — Deep Dive Analysis & Validation (The First 24 Hours)
4. Chapter 4: Phase 3 — Escalation & Communication (Internal & External)
5. Chapter 5: Phase 4 — Eradication, Recovery, and The Feedback Loop

 CyberDudeBivash’s Recommended IR Stack:  XDR & IR Services (Kaspersky) •   CISSP/CISM Leadership Training (Edureka) •   Admin MFA (YubiKey)

Chapter 1: The ‘Unknown Unknown’ — The Challenge of a Suspected Zero-Day

Your threat hunting team just found something. It’s malicious, it’s evasive, and it doesn’t match any signature, CVE, or threat intelligence report on the planet. This is the “Oh S***” moment for any CISO. You might be the first organization in the world to discover a new zero-day exploit. Your standard incident response plan, built for known ransomware or malware, is now inadequate. Reacting incorrectly can tip off the attacker, destroy critical forensic evidence, or cause unnecessary business disruption.

What you need is a specific, pre-defined playbook for handling this “unknown unknown.” This guide provides that framework, transforming a moment of chaos into a controlled, professional process.

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Chapter 2: Phase 1 — Triage & Containment (The First 30 Minutes)

The immediate priority is to stop the bleeding and preserve the evidence.

1. Declare a Major Incident: The frontline analyst who made the discovery immediately escalates to the IR Lead or SOC Manager.
2. Isolate, Do Not Eradicate:** Using your **EDR platform**, immediately isolate the affected host(s) from the network. Do NOT shut down, reboot, or wipe the machine. The goal is containment and evidence preservation.
3. **Preserve Volatile Memory:** The most critical evidence of a sophisticated, in-memory threat exists in the RAM. Immediately perform a live memory acquisition of the isolated host.
4. **Acquire Disk Image:** After the memory dump is complete, take a full forensic disk image of the host.
5. **Gather Logs:** Collect all relevant logs from the host, the firewall, and any other systems it was communicating with.

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Chapter 3: Phase 2 — Deep Dive Analysis & Validation (The First 24 Hours)

Now that the immediate threat is contained, the goal is to prove your hypothesis: is this truly a zero-day?

• **Forensic Analysis:** Your senior IR team or a third-party expert begins analyzing the memory dump and disk image. They will use tools like Volatility to find the malicious processes, injected code, and network artifacts.
• **Malware Reverse Engineering:** Any discovered executables or shellcode must be reverse-engineered to understand their capabilities, infrastructure, and, crucially, the exploit used to deliver them.
• **Enterprise-Wide Threat Hunting:** Based on the TTPs discovered in the forensic analysis, your threat hunting team now queries your entire enterprise for the same indicators. Is this an isolated incident, or a widespread campaign? This is the core loop of our **Zero-Day Defense Matrix**.

 Expertise is Key: This level of analysis requires elite skills. To build this capability in-house, invest in your team. **Edureka’s Advanced Malware Analysis and Reverse Engineering courses** provide the deep technical knowledge required for this work.  

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Chapter 4: Phase 3 — Escalation & Communication (Internal & External)

Once you have a high degree of confidence that you have discovered a novel threat, a structured communication plan is essential.

Internal Escalation Path:

1. SOC Manager to CISO:** The SOC Manager provides a concise, technical briefing to the CISO.
2. **CISO to Executive Team & Legal:** The CISO translates the technical findings into business risk, briefing the CIO, CEO, and General Counsel. All further communication should be managed in coordination with legal counsel.

External Communication Path:

• **Engage Third-Party IR:** If not already engaged, now is the time to bring in your pre-retained incident response firm for third-party validation and assistance.
• **Responsible Disclosure to the Vendor:** Work through your pre-defined process to securely and confidentially report your findings to the affected software or hardware vendor. This allows them to begin developing a patch.
• **Government/Industry Sharing:** Depending on your industry and regulatory requirements, you may need to share indicators with your ISAC or relevant government agencies like CISA.

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Chapter 5: Phase 4 — Eradication, Recovery, and The Feedback Loop

Only after the vulnerability is understood and the full scope of the compromise is known do you move to eradication.

1. **Eradication & Recovery:** Rebuild the compromised systems from a known-good state and, once available, apply the vendor’s emergency patch.
2. **The Feedback Loop:** This is the most important step for long-term resilience. The unique IOCs and TTPs you discovered must be codified into new, automated detection rules in your SIEM, EDR, and other security tools. Your zero-day is now a “known” threat.

By having a playbook for this entire process, you transform a moment of potential chaos into a structured, professional, and controlled incident response that not only mitigates the immediate threat but also permanently matures your security posture.

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About the Author

CyberDudeBivash is a cybersecurity strategist with 15+ years in incident response, threat hunting, and building enterprise security programs, advising CISOs across APAC. [Last Updated: October 03, 2025]

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