Anthropic-Cybersecurity-Skills/skills/hunting-for-spearphishing-indicators/SKILL.md

name, description, domain, subdomain, tags, version, author, license, d3fend_techniques, nist_csf, mitre_attack, mitre_f3

name	description	domain	subdomain	tags	version	author	license	d3fend_techniques	nist_csf	mitre_attack	mitre_f3
hunting-for-spearphishing-indicators	Hunt for spearphishing campaign indicators across email logs, endpoint telemetry, and network data to detect targeted email attacks.	cybersecurity	threat-hunting	threat-hunting mitre-attack spearphishing initial-access email-security t1566 proactive-detection	1.0	mahipal	Apache-2.0	File Metadata Consistency Validation Application Protocol Command Analysis Identifier Analysis Content Format Conversion Message Analysis	DE.CM-01 DE.AE-02 DE.AE-07 ID.RA-05	T1046 T1057 T1082 T1083 T1566	version tactics techniques 1.1 reconnaissance initial-access resource-development id name tactic source T1660 Phishing initial-access attack id name tactic source T1598 Phishing for Information reconnaissance attack id name tactic source T1593 Search Open Websites/Domains reconnaissance attack id name tactic source F1031 Impersonate Account Holder initial-access f3 id name tactic source F1020.002 Create Fake Materials: Fake Website resource-development f3

Hunting For Spearphishing Indicators

When to Use

• When proactively hunting for indicators of hunting for spearphishing indicators in the environment
• After threat intelligence indicates active campaigns using these techniques
• During incident response to scope compromise related to these techniques
• When EDR or SIEM alerts trigger on related indicators
• During periodic security assessments and purple team exercises

Prerequisites

• EDR platform with process and network telemetry (CrowdStrike, MDE, SentinelOne)
• SIEM with relevant log data ingested (Splunk, Elastic, Sentinel)
• Sysmon deployed with comprehensive configuration
• Windows Security Event Log forwarding enabled
• Threat intelligence feeds for IOC correlation

Workflow

1. Formulate Hypothesis: Define a testable hypothesis based on threat intelligence or ATT&CK gap analysis.
2. Identify Data Sources: Determine which logs and telemetry are needed to validate or refute the hypothesis.
3. Execute Queries: Run detection queries against SIEM and EDR platforms to collect relevant events.
4. Analyze Results: Examine query results for anomalies, correlating across multiple data sources.
5. Validate Findings: Distinguish true positives from false positives through contextual analysis.
6. Correlate Activity: Link findings to broader attack chains and threat actor TTPs.
7. Document and Report: Record findings, update detection rules, and recommend response actions.

Key Concepts

Concept	Description
T1566.001	Spearphishing Attachment
T1566.002	Spearphishing Link
T1566.003	Spearphishing via Service

Tools & Systems

Tool	Purpose
CrowdStrike Falcon	EDR telemetry and threat detection
Microsoft Defender for Endpoint	Advanced hunting with KQL
Splunk Enterprise	SIEM log analysis with SPL queries
Elastic Security	Detection rules and investigation timeline
Sysmon	Detailed Windows event monitoring
Velociraptor	Endpoint artifact collection and hunting
Sigma Rules	Cross-platform detection rule format

Common Scenarios

1. Scenario 1: Macro-enabled Excel executing PowerShell downloader
2. Scenario 2: HTML smuggling delivering ISO with LNK payload
3. Scenario 3: Credential harvesting link as SharePoint notification
4. Scenario 4: QR code phishing in PDF attachment

Output Format

Hunt ID: TH-HUNTIN-[DATE]-[SEQ]
Technique: T1566.001
Host: [Hostname]
User: [Account context]
Evidence: [Log entries, process trees, network data]
Risk Level: [Critical/High/Medium/Low]
Confidence: [High/Medium/Low]
Recommended Action: [Containment, investigation, monitoring]