Analyzing Threat Intelligence Feeds

When to Use

Use this skill when:

• Ingesting new commercial or OSINT threat feeds and assessing their signal-to-noise ratio
• Normalizing heterogeneous IOC formats (STIX 2.1, OpenIOC, YARA, Sigma) into a unified schema
• Evaluating feed freshness, fidelity, and relevance to the organization's threat profile
• Building automated enrichment pipelines that correlate IOCs against SIEM events

Do not use this skill for raw packet capture analysis or live incident triage without first establishing a CTI baseline.

Prerequisites

• Access to a Threat Intelligence Platform (TIP) such as ThreatConnect, MISP, or OpenCTI
• API keys for at least one commercial feed (Recorded Future, Mandiant Advantage, or VirusTotal Enterprise)
• TAXII 2.1 client library (taxii2-client Python package or equivalent)
• Role with read/write permissions to the TIP's indicator database

Workflow

Step 1: Enumerate and Prioritize Feed Sources

List all available feeds categorized by type (commercial, government, ISAC, OSINT):

• Commercial: Recorded Future, Mandiant Advantage, CrowdStrike Falcon Intelligence
• Government: CISA AIS (Automated Indicator Sharing), FBI InfraGard, MS-ISAC
• OSINT: AlienVault OTX, Abuse.ch, PhishTank, Emerging Threats

Score each feed on: update frequency, historical accuracy rate, coverage of your sector, and attribution depth. Use a weighted scoring matrix with criteria from NIST SP 800-150 (Guide to Cyber Threat Information Sharing).

Step 2: Ingest via TAXII 2.1 or API

For TAXII-enabled feeds:

taxii2-client discover https://feed.example.com/taxii/
taxii2-client get-collection --collection-id <id> --since 2024-01-01

For REST API feeds (e.g., Recorded Future):

• Query /v2/indicator/search with risk_score_min=65 to filter low-confidence IOCs
• Apply rate limiting and exponential backoff for API resilience

Step 3: Normalize to STIX 2.1

Convert each IOC to STIX 2.1 objects using the OASIS standard schema:

• IP address → indicator object with pattern: "[ipv4-addr:value = '...']"
• Domain → indicator with pattern: "[domain-name:value = '...']"
• File hash → indicator with pattern: "[file:hashes.SHA-256 = '...']"

Attach relationship objects linking indicators to threat-actor or malware objects. Use confidence field (0–100) based on source fidelity rating.

Step 4: Deduplicate and Enrich

Run deduplication against existing TIP database using normalized value + type as composite key. Enrich surviving IOCs:

• VirusTotal: detection ratio, sandbox behavior reports
• PassiveTotal (RiskIQ): WHOIS history, passive DNS, SSL certificate chains
• Shodan: banner data, open ports, geographic location

Step 5: Distribute to Consuming Systems

Export enriched indicators via TAXII 2.1 push to SIEM (Splunk, Microsoft Sentinel), firewalls (Palo Alto XSOAR playbooks), and EDR platforms. Set TTL (time-to-live) per indicator type: IP addresses 30 days, domains 90 days, file hashes 1 year.

Key Concepts

Term	Definition
STIX 2.1	Structured Threat Information Expression — OASIS standard JSON schema for CTI objects including indicators, threat actors, campaigns, and relationships
TAXII 2.1	Trusted Automated eXchange of Intelligence Information — HTTPS-based protocol for sharing STIX content between servers and clients
IOC	Indicator of Compromise — observable artifact (IP, domain, hash, URL) that indicates a system may have been breached
TLP	Traffic Light Protocol — color-coded classification (RED/AMBER/GREEN/WHITE) defining sharing restrictions for CTI
Confidence Score	Numeric value (0–100 in STIX) reflecting the producer's certainty about an indicator's malicious attribution
Feed Fidelity	Historical accuracy rate of a feed measured by true positive rate in production detections

Tools & Systems

• ThreatConnect TC Exchange: Aggregates 100+ commercial and OSINT feeds; provides automated playbooks for IOC enrichment
• MISP (Malware Information Sharing Platform): Open-source TIP supporting STIX/TAXII; widely used by ISACs and government CERTs
• OpenCTI: Open-source platform with native MITRE ATT&CK integration and graph-based relationship visualization
• Recorded Future: Commercial feed with AI-powered risk scoring and real-time dark web monitoring
• taxii2-client: Python library for TAXII 2.0/2.1 client operations (pip install taxii2-client)
• PyMISP: Python API for MISP feed management and IOC submission

Common Pitfalls

• IOC age staleness: IP addresses and domains rotate frequently; applying 1-year-old IOCs generates false positives. Enforce TTL policies.
• Missing context: Blocking an IOC without understanding the associated campaign or adversary can disrupt legitimate business traffic (e.g., CDN IPs shared with malicious actors).
• Feed overlap without deduplication: Ingesting the same IOC from five feeds without deduplication inflates indicator counts and SIEM rule complexity.
• TLP violation: Redistributing RED-classified intelligence outside authorized boundaries violates sharing agreements and trust relationships.
• Over-blocking on low-confidence indicators: Indicators with confidence below 50 should trigger detection-only rules, not blocking, to avoid operational disruption.