Performing Cloud Forensics With AWS Cloudtrail

Performing Cloud Forensics with AWS CloudTrail

When to Use

• When investigating suspected AWS account compromise
• After detecting unauthorized API calls or credential exposure
• During incident response involving cloud infrastructure
• When analyzing S3 data exfiltration or IAM privilege escalation
• For post-incident forensic timeline reconstruction

Detection Gaps & Validation

• LookupEvents won't show data-plane activity: cloudtrail:LookupEvents returns only management events for the last 90 days. S3 GetObject, PutObject, and Lambda Invoke are data events, absent unless data event logging was enabled before the incident - pivot to S3 server access logs / Athena to prove exfiltration.
• Single-region or non-org trails leave blind spots: an attacker operating in an unmonitored region produces no events in a region-scoped trail. Confirm the trail is multi-region and org-wide via aws cloudtrail describe-trails (IsMultiRegionTrail, IsOrganizationTrail).
• Check for anti-forensics first: hunt StopLogging, UpdateTrail, DeleteTrail, and PutEventSelectors events - an attacker may have blinded logging. Then run aws cloudtrail validate-logs against the digest files to detect deletion/tampering.
• Attribute actions correctly: track both userIdentity.accessKeyId and sessionContext.sessionIssuer - an AssumeRole issues temporary keys (ASIA...), so following only the original key loses the attacker after the pivot.
• AccessDenied is signal, not noise: denied calls are still logged and reveal recon and failed escalation; don't filter them out of the timeline.
• How to confirm a finding: corroborate the CloudTrail timeline against VPC Flow Logs (same source IP) and the resource's own logs, and remember every eventTime is UTC when sequencing events.
• Don't conclude "no compromise" until data events are accounted for (or shown to have been disabled), the trail covered all regions, and logging-tamper events plus digest validation have been checked.

Prerequisites

• AWS account with CloudTrail enabled (management and data events)
• IAM permissions for cloudtrail:LookupEvents, s3:GetObject, athena:StartQueryExecution
• boto3 Python SDK installed
• CloudTrail logs delivered to S3 with optional Athena table configured
• AWS CLI configured with appropriate credentials

Workflow

1. Scope Investigation: Identify timeframe, affected accounts, and compromised credentials.
2. Query CloudTrail: Use boto3 lookup_events or Athena to retrieve relevant API events.
3. Filter by Indicators: Search for suspicious user agents, source IPs, and event names.
4. Reconstruct Timeline: Build chronological sequence of attacker actions from API calls.
5. Analyze Access Patterns: Identify data access, IAM changes, and resource modifications.
6. Identify Persistence: Check for new IAM users, access keys, roles, or Lambda functions.
7. Generate Report: Produce forensic timeline with findings and remediation steps.

Key Concepts

Tools & Systems

Output Format

Forensic Report: AWS-IR-[DATE]-[SEQ]
Account: [AWS Account ID]
Timeframe: [Start] to [End]
Compromised Credentials: [Access Key IDs]
Suspicious Events: [Count]
Source IPs: [List of attacker IPs]
Actions Taken: [API calls by attacker]
Data Accessed: [S3 objects, secrets, etc.]
Persistence Mechanisms: [New users, keys, roles]