Chain of custody documents the complete history of evidence — who collected it, how it was stored, and who had access. In cloud forensics, where evidence is API-sourced and inherently mutable, maintaining an unbroken chain requires specific technical and procedural controls.
Sign in to mark this article as read and track your progress.
Chain of custody (CoC) is the chronological documentation that shows the seizure, custody, control, transfer, analysis, and disposition of physical or electronic evidence. In court, a break in the chain of custody can cause evidence to be ruled inadmissible — the opposing party can argue that the evidence was tampered with during the gap.
In traditional digital forensics, CoC was established through:
In cloud forensics, you almost never physically possess the storage medium. The cloud provider holds the disks. You receive API responses, log exports, and snapshots. Establishing equivalent CoC requires adapting the procedures to the cloud context.
| Property | Traditional Digital Forensics | Cloud Forensics |
|---|---|---|
| Evidence source | Physical device seized by investigator | API call returns log data from provider's infrastructure |
| Integrity baseline | MD5/SHA-1 hash of physical media sectors | Hash of exported log file or snapshot |
| Collection verification | Write-blocker hardware prevents modification | No physical control; provider's integrity guarantees must be trusted |
| Provider logs | N/A | Provider (AWS, Azure) has hypervisor-level logs not accessible to customer |
| Multi-tenancy | N/A | Evidence on shared infrastructure may interleave with other customers' data |
| Time zones | Physical device clock | AWS CloudTrail timestamps are UTC; must document timezone handling |
AWS CloudTrail generates a digest file every hour that contains the SHA-256 hashes of all log files delivered in that hour, signed with a private key held by AWS. This provides cryptographic proof that log files have not been modified after delivery.
# Validate CloudTrail log integrity
aws cloudtrail validate-logs \
--trail-arn arn:aws:cloudtrail:ap-south-1:123456789012:trail/management-events \
--start-time "2024-07-01T00:00:00Z" \
--end-time "2024-07-03T23:59:59Z"
# Output:
# Validating log files for trail arn:aws:cloudtrail:...
# 2024/07/01/... hash validation passed
# 2024/07/02/... hash validation passed
# Validation completed. 2 log files validated, 0 errors.
Include the validation output in the evidence record. It establishes that the logs are in the same state as when AWS delivered them.
All evidence collected during an investigation must be stored in a dedicated forensic S3 bucket with:
# Create forensic evidence bucket
aws s3api create-bucket \
--bucket ir-forensics-2024-07-03-incident-001 \
--create-bucket-configuration LocationConstraint=ap-south-1 \
--object-lock-enabled-for-bucket
# Set compliance retention
aws s3api put-object-lock-configuration \
--bucket ir-forensics-2024-07-03-incident-001 \
--object-lock-configuration '{
"ObjectLockEnabled": "Enabled",
"Rule": {"DefaultRetention": {"Mode": "COMPLIANCE", "Days": 365}}
}'
Every item of evidence must be recorded in an evidence manifest at the time of collection:
| Field | Example Value |
|---|---|
| Evidence ID | EV-2024-0703-001 |
| Item | CloudTrail logs, ap-south-1, 2024-07-01 to 2024-07-03 |
| Collection method | aws s3 sync s3://cloudtrail-logs/AWSLogs/… → forensic bucket |
| Collected by | Investigator: Priya Sharma (employee ID 4521) |
| Date/time (UTC) | 2024-07-03T08:42:15Z |
| SHA-256 hash | d8e8fca2dc0f896fd7cb4cb0031ba249... |
| Storage location | s3://ir-forensics-2024-07-03-incident-001/cloudtrail/ |
| Access log | CloudWatch Logs group: /forensic/access-log |
All cloud log timestamps are in UTC. The evidence record must explicitly document:
The Scientific Working Group on Digital Evidence (SWGDE) has published guidelines on cloud evidence collection. Key principles:
Some evidence — hypervisor logs, physical access records, deleted object recovery — is available only from the cloud provider. The process:
aws-security@amazon.com for law enforcement requests. Full details at AWS Law Enforcement Guidelines.Document all requests to providers, including date of request, specific evidence requested, and response received.