🛡️ Elite Defender’s Guide • Threat Hunting

      Threat Hunting Hypothesis: A Defender’s Guide to Finding an Unknown Zero-Day Exploit in Your Web Servers    

By CyberDudeBivash • October 02, 2025 • SOC & Threat Hunting Playbook

 cyberdudebivash.com |       cyberbivash.blogspot.com 

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

 Threat Hunting Playbook: Table of Contents 

1. Chapter 1: The Art of the Hunt — Moving Beyond Alerts
2. Chapter 2: Step 1 — Formulating the Hypothesis
3. Chapter 3: Step 2 — Executing the Hunt (The ‘Golden Query’)
4. Chapter 4: Step 3 — The Outcome & Automating Your Discovery

Chapter 1: The Art of the Hunt — Moving Beyond Alerts

A Security Operations Center (SOC) that only responds to automated alerts is always one step behind the adversary. This is a reactive posture. **Threat Hunting**, by contrast, is the proactive and iterative search for threats that have evaded your existing security controls. It is a mindset that assumes you are already compromised. A threat hunter is not a security guard waiting for an alarm; they are a detective actively looking for clues.

The foundation of any effective hunt is a clear, testable **hypothesis**. Instead of boiling the ocean of data, you start with a specific, educated guess about what an attacker might be doing, and then you search for the evidence to prove or disprove it.

Chapter 2: Step 1 — Formulating the Hypothesis

For this exercise, our hypothesis will target the most common critical threat to internet-facing infrastructure. We will state it clearly:

Hypothesis: “A sophisticated adversary is exploiting an unknown, zero-day Remote Code Execution (RCE) vulnerability in our internet-facing web servers. This initial exploit will result in the web server process spawning an anomalous child process, such as a command shell or a scripting engine, which will be visible on the endpoint even if the initial network request is obfuscated or encrypted.”

This hypothesis is powerful because it’s specific, it’s testable, and it focuses on a high-fidelity, post-exploitation behavior that is extremely difficult for an attacker to hide.

Chapter 3: Step 2 — Executing the Hunt (The ‘Golden Query’)

To test our hypothesis, we need to find all instances of a web server process spawning a child process. This is where an **Endpoint Detection and Response (EDR)** solution is non-negotiable. A SIEM can’t see this; only an EDR with deep process-level visibility can.

The “Golden Query” for Web Server Compromise:

In your EDR’s threat hunting interface, you will run a query that looks conceptually like this:

SELECT parent_process_name, process_name, command_line
FROM process_events
WHERE parent_process_name IN ('w3wp.exe', 'nginx.exe', 'httpd', 'apache2')
AND process_name IN ('cmd.exe', 'powershell.exe', '/bin/bash', '/bin/sh', 'whoami', 'certutil.exe', 'cscript.exe')

This query searches for all process creation events where the parent is a common web server process and the child is a common shell or scripting engine. **For a healthy, properly configured web server, the result of this query should be ZERO.**

If this query returns even a single event, it is a critical indicator of compromise that requires immediate investigation. You have likely just found an active breach, such as the kind of compromise caused by the **SessionHunter IIS malware**.

 Visibility is Key: You cannot hunt what you cannot see. This entire playbook is impossible without a modern EDR. A platform like **Kaspersky EDR** provides the necessary telemetry and the powerful query interface to execute these advanced hunts. Learn more in our **EDR Face-Off**.  

Chapter 4: Step 3 — The Outcome & Automating Your Discovery

The result of a hunt is always a win, regardless of the outcome.

• **If your hypothesis is proven (You find a malicious process):** Congratulations, you have just found a real threat that your automated defenses missed. You immediately pivot from threat hunting to your **Incident Response** process to contain and eradicate the threat.
• **If your hypothesis is disproven (You find nothing):** Congratulations, this is also a success. You have validated that your baseline is clean for this specific threat vector, and you have practiced and refined your hunting skills.

The Final Step: Automation

Your work is not done. Now that you have created and validated a high-fidelity hunting query, you should turn it into an automated detection rule. Take your “Golden Query” and configure it as a custom, high-severity alert in your EDR or SIEM. The next time this specific TTP occurs, you will get an immediate, automated alert. You have successfully taken an “unknown unknown” and turned it into a “known unknown.” This is the core feedback loop of a mature **Security Operations Center**.

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About the Author

CyberDudeBivash is a cybersecurity strategist with 15+ years in threat hunting, incident response, and building elite Security Operations Centers, advising CISOs across APAC. [Last Updated: October 02, 2025]

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