Outbound Transfer Blocking

1. Prerequisites

• Confirmed or suspected active data exfiltration activity
• Completion of Outbound Traffic Analysis
• Access to firewall management platforms
• Access to proxy management platforms
• Access to DNS filtering platforms
• Access to cloud security tooling
• Access to network security tooling
• Access to SIEM
• List of identified:
  • Destination IP addresses
  • Domains
  • URLs
  • Cloud storage providers
  • SaaS platforms
• Incident Commander approval for containment actions (if required)

2. Step-by-Step Instructions

1. Identify Active Exfiltration Paths

   • Review investigation findings.
   • Identify:
     • Destination IP addresses
     • Domains
     • URLs
     • Cloud storage services
     • SaaS applications
     • Transfer protocols
   • Document all identified transfer paths.

2. Validate Containment Scope

   • Determine:
     • Affected users
     • Affected systems
     • Business impact of blocking actions
   • Confirm containment scope with the Incident Commander.

3. Block Network Destinations

   • Implement blocks for identified:
     • IP addresses
     • Domains
     • URLs
   • Use:
     • Firewalls
     • Secure Web Gateways
     • Proxies
     • DNS filtering solutions
   • Validate successful deployment.

4. Block Cloud Storage Services

   • Restrict access to identified cloud storage providers.
   • Block:
     • Upload functionality
     • Synchronisation services
     • Web-based transfer mechanisms
   • Validate enforcement across affected assets.

5. Restrict SaaS-Based Transfers

   • Disable or restrict:
     • External sharing
     • Public links
     • Guest access
     • Unauthorised file transfers
   • Document all changes made.

6. Disable Unauthorised Transfer Mechanisms

   • Restrict:
     • FTP
     • SFTP
     • SCP
     • Remote administration tools
     • File synchronisation utilities
   • Remove or disable unauthorised transfer channels where possible.

7. Monitor for Continued Transfer Attempts

   • Review:
     • Firewall logs
     • Proxy logs
     • DNS logs
     • Cloud audit logs
   • Identify continued attempts to communicate with blocked destinations.

8. Validate Containment Effectiveness

   • Confirm:
     • Active transfers have ceased
     • Destinations are unreachable
     • Upload attempts are blocked
     • Sharing restrictions are functioning correctly
   • Document validation results.

9. Document Containment Actions

   • Record:
     • Blocks implemented
     • Systems affected
     • Services restricted
     • Time of implementation
     • Validation results
   • Preserve supporting evidence.

10. Escalate and Hand Off

    • Provide containment status to the Incident Commander.
    • Coordinate with:
      • Recovery activities
      • Sensitive Data Impact Assessment
      • Regulatory and Legal Coordination
    • Update the incident record with all actions performed.

3. Post-Action

• Ensure all implemented blocks are documented.
• Ensure all containment actions are recorded in the incident record.
• Preserve logs demonstrating successful containment.
• Continue monitoring for attempted bypass activity.
• Coordinate with recovery teams before removing temporary restrictions.
• Participate in post-incident review activities as required.

Contributor

Vishal Thakur
GitHub: https://github.com/malienist

Contributed to the Arcana Incident Response Documentation Framework.