SPLK-5001 Threat Hunting and Remediation

Threat Hunting and Remediation Detailed Explanation

1. Threat Hunting Overview

Threat hunting is the proactive practice of searching through networks, endpoints, and data to detect threats that have bypassed existing security defenses.

Key Characteristics:

• Proactive:
  Instead of waiting for security tools to trigger alarms, threat hunters actively search for hidden threats.

• Hypothesis-Driven:
  Threat hunters usually start with an idea or hypothesis about what kind of threat might exist, based on threat intelligence, known attacker behaviors (TTPs), or observed anomalies.

• Iterative and Analytical:
  Threat hunting is not a one-time event. It involves cycles of asking questions, exploring data, testing hypotheses, and refining the search based on findings.

Summary:
Threat hunting helps organizations find sophisticated attacks early, even before damage is done.

2. Threat Hunting Methodologies

Different methods can be used for effective threat hunting:

Intel-Driven Hunting

Uses external or internal threat intelligence to guide the search.

Focus:

• Searching for known indicators of compromise (IOCs) such as malicious IP addresses, domains, file hashes, or attack signatures.

Example:
Hunting for connections to an IP address flagged in a threat intelligence report.

TTP-Based Hunting (MITRE ATT&CK Driven)

Focuses on detecting attacker behaviors rather than specific indicators.

TTP stands for:

• Tactics: The attacker's goals

• Techniques: How they achieve those goals

• Procedures: The specific ways they carry out techniques

By hunting for behaviors, organizations can detect attacks even if specific IOCs change.

Example:
Hunting for signs of credential dumping, regardless of which tool the attacker used.

Anomaly-Based Hunting

Focuses on identifying deviations from normal behavior.

Steps:

• Define what is "normal" for users, systems, and network traffic.

• Search for activities that break those patterns.

Example:
A user who typically logs in during business hours suddenly logs in at 3 AM from a foreign country.

Situational Hunting

Triggered by specific external or internal events.

Examples of triggers:

• A newly discovered software vulnerability

• Major news about an industry-wide cyberattack

• Internal detection of suspicious activity

In such cases, organizations conduct focused hunts related to the specific threat.

Summary:
Using multiple methodologies allows hunters to catch both known and unknown threats.

3. The Threat Hunting Process

The threat hunting process typically follows these steps:

Trigger

A hypothesis or lead that starts the hunt.

Sources of triggers:

• Threat intelligence

• Anomalous behavior observed

• Known vulnerabilities

• Suspicious system alerts

Example:
News about a new ransomware strain leads a team to hunt for signs of related infections.

Investigation

Deep exploration of the environment to search for signs of malicious activity.

Methods:

• Running SPL queries

• Pivoting from one suspicious event to related activities

• Analyzing linked data across systems

Example:
Investigating multiple failed login attempts followed by a successful one.

Pattern and Artifact Identification

Discovering new attack patterns or malicious artifacts.

Patterns and artifacts include:

• New types of malware files

• Specific IP addresses or domains used by attackers

• New techniques attackers are using

Once discovered, they can be used to update detection capabilities.

Remediation or Escalation

If a real threat is found:

• Immediate action must be taken to contain and eliminate the threat.

• Serious incidents may be escalated to the incident response team for further handling.

Knowledge Sharing

Document findings to:

• Improve detection rules

• Educate security teams

• Strengthen the organization's defenses

Example:
Adding newly discovered malware hashes to threat intelligence feeds.

Example Hypothesis

Credential abuse may occur through repeated login failures across multiple servers.

In Splunk, a search to test this hypothesis:

index=security sourcetype=wineventlog:security (EventCode=4625 OR EventCode=4624)
| stats count by user, src_ip
| where count > 50

This search finds users and source IPs with unusually high numbers of authentication events.

4. Threat Hunting Tools and Techniques in Splunk

Splunk provides powerful tools to assist threat hunters:

Data Models

Data models organize and accelerate large datasets.

Using accelerated data models allows:

• Faster searches across huge volumes of security event data.

• Consistent field names and data structure for easier analysis.

Example:
Using the Authentication data model to quickly find login anomalies.

Risk-Based Alerting

Instead of treating every alert separately, risk-based alerting:

• Combines the risk from multiple small events

• Focuses attention on entities (users, devices) with the highest total risk

Benefits:

• Reduces alert fatigue

• Prioritizes the most dangerous threats

Splunk Enterprise Security (ES)

Splunk ES is an advanced security platform that provides:

• Threat Activity dashboards

• Risk Analysis dashboards

• Incident Review dashboards

These dashboards help hunters quickly spot suspicious behaviors and coordinate responses.

Use of Lookups

Lookups allow searches to be enriched with external or internal data, such as:

• Lists of known bad IP addresses

• Known malware file hashes

• Suspicious domains

Using lookups speeds up and improves the accuracy of threat hunting.

Macro-Driven Modular Searches

SPL macros are reusable chunks of SPL code.

Benefits of using macros:

• Build flexible searches

• Save time when creating complex queries

• Maintain consistency across different hunts

Example:
Creating a macro to search for suspicious user behavior across multiple systems.

5. Remediation Overview

When a threat is found, remediation is the process of eliminating the threat and restoring the environment to a safe state.

Steps involved:

Identification

Confirm that the threat is real and understand its full scope.

Activities:

• Determine which systems are affected

• Understand how the threat entered

Containment

Stop the threat from spreading.

Common actions:

• Disconnect infected machines from the network

• Disable compromised user accounts

• Block malicious IP addresses

Eradication

Remove the threat completely.

Actions include:

• Deleting malware

• Closing vulnerabilities

• Changing stolen passwords

Recovery

Restore normal operations securely.

Steps:

• Rebuild or restore clean systems

• Verify systems are free of infections

• Monitor closely for signs of re-infection

Post-Mortem Review

Analyze what happened and why.

Objectives:

• Understand the root cause

• Identify weaknesses

• Update defenses and response plans

Automation in Remediation

Modern organizations use SOAR (Security Orchestration, Automation, and Response) tools like Splunk SOAR to automate parts of remediation.

Common automated actions:

• Blocking malicious IP addresses in firewalls

• Disabling compromised accounts immediately

• Triggering endpoint antivirus scans

Example Automated Playbook

• An alert is triggered.

• The system automatically enriches the alert with threat intelligence.

• If the IP address is confirmed malicious:

  • Quarantine the infected device.

  • Notify the Security Operations Center (SOC).

Automation saves time and reduces the risk of human error during a security incident.

Threat Hunting and Remediation (Additional Content)

1. Hunting Maturity Model (HMM) in Threat Hunting

The Hunting Maturity Model (HMM) is a framework that describes an organization’s capabilities and progression in conducting threat hunting activities.

Key Characteristics:

• Provides a structured way to assess and improve threat hunting capabilities over time.

• Helps organizations understand where they currently stand and what steps are needed to become more proactive and advanced.

The HMM defines several levels of maturity:

• Initial:
  Hunting is reactive, and detection relies solely on alerts from security tools. No formalized hunting processes exist.

• Minimal:
  Some manual, ad-hoc hunting efforts are performed, usually without defined processes or automation.

• Procedural:
  Hunting follows documented, repeatable procedures, often based on known threats or attack patterns.

• Innovative:
  Hunters proactively develop new detection methods and leverage advanced analytics and threat intelligence.

• Leading:
  Threat hunting is fully integrated into the security operations lifecycle. There is continuous innovation, use of machine learning, and close alignment with business risk priorities.

Purpose:

• To encourage a shift from reactive to proactive threat detection.

• To guide investment in tools, skills, and processes that improve hunting effectiveness.

Summary:
The Hunting Maturity Model (HMM) helps organizations evaluate and enhance their threat hunting capabilities by progressing through defined maturity levels, from initial reactive detection to proactive and innovative security practices.

2. Prioritizing Crown Jewels During Remediation

In the context of remediation, especially after a cybersecurity incident, it is crucial to prioritize the protection of an organization's crown jewels — its most critical assets.

Key Characteristics:

• Crown jewels refer to the systems, data, and services that are vital to the organization’s core operations and strategic objectives.

• These assets typically include:

  • Financial systems.

  • Customer databases containing sensitive information.

  • Intellectual property repositories.

  • Mission-critical applications.

Why Prioritize Crown Jewels:

• Attacks on crown jewels can cause the most severe financial, reputational, and operational damage.

• Resources during incident response are often limited, requiring careful triage.

• Protecting critical assets first ensures the organization can continue essential business functions even if broader remediation efforts are still ongoing.

Approach:

• Identify crown jewels as part of the organization’s pre-incident planning.

• In the event of a breach, prioritize containment, eradication, and recovery efforts around these key assets.

• Deploy enhanced monitoring and additional security controls around crown jewels during and after the incident.

Example:

• During a ransomware attack, the IT team focuses first on isolating and preserving access to the customer billing database before addressing less critical systems like internal test servers.

Summary:
Effective remediation strategies prioritize safeguarding crown jewels — the assets that are essential to an organization's survival and success — ensuring that the most critical resources are protected first during a security incident.