Agent-Skills.md

Agent Skills: Hunting for Data Exfiltration Indicators

Hunt for data exfiltration through network traffic analysis, detecting unusual data flows, DNS tunneling, cloud storage uploads, and encrypted channel abuse.

UncategorizedID: plurigrid/asi/hunting-for-data-exfiltration-indicators

Repository

plurigrid/asi
plurigridLicense: MIT
165

Install this agent skill to your local

pnpm dlx add-skill https://github.com/plurigrid/asi/tree/HEAD/plugins/asi/skills/hunting-for-data-exfiltration-indicators

Skill Files

Browse the full folder contents for hunting-for-data-exfiltration-indicators.

Download Skill

Loading file tree…

plugins/asi/skills/hunting-for-data-exfiltration-indicators/SKILL.md

Skill Metadata

Name
hunting-for-data-exfiltration-indicators
Description
Hunt for data exfiltration through network traffic analysis, detecting unusual data flows, DNS tunneling, cloud storage uploads, and encrypted channel abuse.

Hunting for Data Exfiltration Indicators

When to Use

  • When hunting for data theft in compromised environments
  • After detecting unusual outbound data volumes or patterns
  • When investigating potential insider threat data theft
  • During incident response to determine what data was stolen
  • When threat intel indicates data exfiltration campaigns targeting your sector

Prerequisites

  • Network proxy/firewall logs with byte-level data transfer metrics
  • DLP solution or CASB with cloud upload visibility
  • DNS query logs for DNS exfiltration detection
  • Email gateway logs for attachment monitoring
  • SIEM with data volume anomaly detection capabilities

Workflow

  1. Define Exfiltration Channels: Identify potential channels (HTTP/S uploads, DNS tunneling, email attachments, cloud storage, removable media, encrypted protocols).
  2. Baseline Normal Data Flows: Establish baseline outbound data transfer volumes per user, host, and destination over a 30-day window.
  3. Detect Volume Anomalies: Identify hosts or users transferring significantly more data than baseline to external destinations.
  4. Analyze Transfer Destinations: Check destination domains/IPs against threat intel, identify newly registered domains, personal cloud storage, and foreign infrastructure.
  5. Inspect Protocol Abuse: Look for DNS tunneling (large/frequent TXT queries), ICMP tunneling, or data hidden in allowed protocols.
  6. Correlate with File Access: Link exfiltration indicators to file access events on sensitive file shares, databases, or repositories.
  7. Report and Contain: Document findings with evidence, estimate data exposure, and recommend containment actions.

Key Concepts

| Concept | Description | |---------|-------------| | T1041 | Exfiltration Over C2 Channel | | T1048 | Exfiltration Over Alternative Protocol | | T1048.001 | Exfiltration Over Symmetric Encrypted Non-C2 | | T1048.002 | Exfiltration Over Asymmetric Encrypted Non-C2 | | T1048.003 | Exfiltration Over Unencrypted/Obfuscated Non-C2 | | T1567 | Exfiltration Over Web Service | | T1567.002 | Exfiltration to Cloud Storage | | T1052 | Exfiltration Over Physical Medium | | T1029 | Scheduled Transfer | | T1030 | Data Transfer Size Limits (staging) | | T1537 | Transfer Data to Cloud Account | | T1020 | Automated Exfiltration |

Tools & Systems

| Tool | Purpose | |------|---------| | Splunk | SIEM for data volume analysis and SPL queries | | Zeek | Network metadata for data flow analysis | | Microsoft Defender for Cloud Apps | CASB for cloud exfiltration | | Netskope | Cloud DLP and exfiltration detection | | Suricata | Network IDS for protocol anomaly detection | | RITA | DNS exfiltration and beacon detection | | ExtraHop | Network traffic analysis for data flow |

Common Scenarios

  1. Cloud Storage Exfiltration: User uploads sensitive documents to personal Google Drive or Dropbox via browser.
  2. DNS Tunneling: Malware exfiltrates data encoded in DNS subdomain queries to attacker-controlled nameserver.
  3. HTTPS Upload: Compromised system POSTs large data blobs to C2 server over encrypted HTTPS.
  4. Email Attachment Exfiltration: Insider forwards sensitive documents to personal email accounts.
  5. Staging and Compression: Adversary stages data in compressed archives before slow exfiltration to avoid detection.

Output Format

Hunt ID: TH-EXFIL-[DATE]-[SEQ]
Exfiltration Channel: [HTTP/DNS/Email/Cloud/USB]
Source: [Host/User]
Destination: [Domain/IP/Service]
Data Volume: [Bytes/MB/GB]
Time Period: [Start - End]
Protocol: [HTTPS/DNS/SMTP/SMB]
Files Involved: [Count/Types]
Risk Level: [Critical/High/Medium/Low]
Confidence: [High/Medium/Low]