Introduction: The Problem with Reactive Security
In today’s cybersecurity landscape, enterprises deploy powerful detection tools—SIEMs, IDS/IPS, EDRs—that are designed to flag malicious activity based on known signatures, pre-defined rules, or established baselines of “normal” behavior.
These tools are vital, but there’s a catch: they’re only as good as the rules and indicators they’re fed. That means:
- They excel at catching known threats—malware with existing signatures, IPs on blocklists, or behaviors previously catalogued as malicious.
- They struggle with unknown or evolving threats—new attack techniques, insider threats, living-off-the-land attacks, or APT activity designed to evade signature-based detection.
Sophisticated adversaries know this and actively engineer their attacks to blend in with legitimate activity, exploiting the blind spots of traditional security monitoring.
This is why proactive threat hunting has become a necessity—not a luxury. Instead of waiting for alerts, analysts go looking for signs of compromise based on hypotheses, threat intelligence, and deep environmental knowledge.
One of the most effective ways to bring structure and repeatability to this process is through the PEAK Framework.
The PEAK Framework at a Glance
PEAK stands for:
- Prepare – Lay the groundwork for a focused and effective hunt.
- Execute – Carry out the investigation with a mix of analytics, intelligence, and data exploration.
- Act – Confirm findings, respond, and remediate.
- Keep – Preserve knowledge, improve processes, and strengthen detection.
This four-step cycle turns hunting from an ad-hoc activity into a disciplined, intelligence-driven program that continually sharpens an organization’s security posture.
Prepare: Setting the Stage for Success
Threat hunting without preparation is like going fishing without knowing the type of fish, the location, or the bait. Preparation ensures that hunts are focused, relevant, and feasible.
Key elements of Prepare:
- Define the Hunt Hypothesis This is a reasoned assumption that suspicious or malicious activity may be occurring, based on:
- Scope the Hunt Decide:
- Gather Tools & Data Sources A hunter’s toolkit might include:
- Set Objectives & Success Criteria Define what a “win” looks like. Is it detecting a specific attacker technique? Is it validating the environment is clean from a certain threat?
Why it matters: Without this phase, hunts risk becoming endless rabbit holes with no clear value delivered.
Execute: The Art and Science of Hunting
Once prepared, hunters move into active investigation—blending the analytical mindset of a detective with the technical skill of a data scientist.
Core Activities:
- Data Exploration & Filtering Start broad, then narrow:
- Behavior-Based Analysis Move beyond static signatures:
- Correlation with Threat Intelligence
- Hypothesis Testing Try to disprove your hypothesis. If it holds after rigorous testing, your suspicion grows stronger.
Example: Hypothesis: "Service account XYZ is being misused to access sensitive data." Testing: Query logs for activity from that account outside normal working hours, compare with baseline, review authentication sources, and correlate with user activity records.
Act: From Detection to Response
Once suspicious activity is confirmed, the focus shifts to containment and remediation.
Steps in Act phase:
- Validate Findings Ensure there are no false positives by:
- Classify Incident Severity Use the organization’s incident classification matrix to prioritize.
- Respond
- Document Actions Clearly record:
Why it matters: Acting decisively prevents further damage and enables faster recovery.
Keep: Closing the Loop and Getting Better
Threat hunting is only valuable if its lessons feed back into the organization’s broader security strategy.
Key Actions in Keep phase:
- Update Detection Rules Convert findings into SIEM rules, EDR detections, or anomaly models so the same attack is caught automatically in the future.
- Enhance Playbooks Incorporate lessons learned into incident response and threat hunting playbooks.
- Knowledge Sharing Share internally across SOC teams and, where appropriate, with industry sharing groups (e.g., ISACs).
- Measure & Improve Track metrics:
Why it matters: “Keep” transforms one-off hunts into a self-improving cycle of resilience.
Why PEAK Works Better Than Ad-Hoc Hunting
- Structure & Repeatability – Clear stages ensure hunts have direction, purpose, and measurable outcomes.
- Alignment with Business Risk – Starting with a hypothesis rooted in relevant threats ensures resources target high-impact risks.
- Knowledge Retention – “Keep” prevents the loss of valuable lessons, reducing the chance of repeat compromise.
- Improved Detection Over Time – Findings are operationalized into automated detection, raising the organization’s baseline security.
Real-World Example: PEAK in Action
Imagine a financial institution concerned about insider data theft.
- Prepare – Hypothesis: “A privileged user may be exfiltrating sensitive reports outside business hours.” Data sources: DLP logs, VPN logs, file access records.
- Execute – Query logs for after-hours file downloads by privileged accounts, correlate with unusual outbound connections.
- Act – Confirm one account is accessing files without a legitimate work order, and sending them to an unknown external FTP server. Disable account, block IP, initiate HR/legal investigation.
- Keep – Update DLP rules to flag any future after-hours sensitive file access attempts. Share findings with SOC, update insider threat hunting playbook.