Full Report
In the final section of this blog series on uncovering complex hybrid cloud attacks, we’ll share key elements of the response to the real-world sophisticated cloud attack outlined in Part 2.
Analysis Summary
# Incident Report: Sophisticated Hybrid Cloud Attack and Credential Compromise
## Executive Summary
A sophisticated, long-running hybrid cloud attack was uncovered when an engineer noticed missing OS logs on an AWS EC2 instance. Attackers leveraged a compromised privileged IAM user, initially gaining access through suspicious `GetPasswordData` operations, leading to the deployment of reverse shells and the likely exfiltration of sensitive data from RDS databases. A subsequent re-compromise via a newly issued key suggested an insider vector, which was ultimately traced back to a phishing attack targeting an employee's home computer, revealing the full two-year scope of the incident.
## Incident Details
- Discovery Date: Undisclosed (Initial investigation triggered by missing local OS logs)
- Incident Date: Attack spanned a period of almost two years.
- Affected Organization: Victim organization (Identity protected)
- Sector: Undisclosed (Involves AWS cloud infrastructure, EC2, RDS)
- Geography: Undisclosed
## Timeline of Events
### Initial Access
- Date/Time: Preceded the first detection by over a year.
- Vector: Phishing/Social Engineering targeting an employee's personal home computer (revealed later as root cause).
- Details: The initial compromise on the employee's device ultimately led to the compromise of a privileged AWS IAM user.
### Lateral Movement
- Date/Time: Before reverse shell deployment.
- Vector: Use of the compromised IAM user credentials via AWS API calls.
- Details: The compromised IAM user executed `GetPasswordData` operations on target EC2 instances, obtaining local administrator passwords, which then allowed the attackers to deploy reverse shells on the instances.
### Data Exfiltration/Impact
- Date/Time: Occurred over a long period, including a three-day period before the second detection.
- Details: Access to S3 buckets and sensitive RDS databases was identified. **Full scope of data exfiltration remains unknown** due to attacker modifications of audit policies. During the second phase, new sensitive information was successfully exfiltrated from the RDS database over three days.
### Detection & Response
- Date/Time: Initial detection occurred when a cloud engineer noticed missing local OS logs on a production EC2 instance.
- Response details: Forensics on an AMI snapshot revealed reverse shells. Cross-referencing timestamps with retained CloudTrail logs linked back to the `GetPasswordData` activity by the compromised IAM user. Initial remediation involved rotating the compromised IAM user credentials, rotating all privileged AWS credentials, quarantining and recovering compromised EC2 instances, restoring tampered logging policies, and enhancing logging (e.g., VPC Flow Logs).
- **Second Detection:** Several weeks after initial remediation, a newly created SIEM alert triggered on attempted modification of RDS audit policies. Attackers were found to be actively exfiltrating data using the *newly issued* access key for the same compromised IAM user. Root cause investigation pivoted toward a potential insider threat when access to AWS Secrets Manager for the new key appeared normal. The breakthrough came from forensic analysis of the employee's cooperating personal home computer, which showed the initial payload running and communicating with the attacker IP.
## Attack Methodology
- Initial Access: Social engineering/Phishing leading to the compromise of an employee's home device, which provided initial foothold for exploiting cloud credentials.
- Persistence: Reverse shells left on EC2 instances; continued access via compromised IAM user credentials (both original and newly issued key).
- Privilege Escalation: Not explicitly detailed, but the IAM user already possessed high privileges. Accessing local admin passwords via `GetPasswordData` allowed for root-level control on the EC2 instances.
- Defense Evasion: Attackers modified (deleted/altered) local OS logs on EC2 instances. Attackers also modified audit policies on RDS databases to cover their tracks.
- Credential Access: **OS level**: Obtaining local admin passwords via `GetPasswordData`. **Cloud Level**: Compromise of a privileged IAM user credential set, which was subsequently re-compromised even after rotation.
- Discovery: Attackers used the compromised cloud access to pivot and identify valuable resources (S3, RDS).
- Lateral Movement: Movement between on-premises (employee's home PC) and the hybrid cloud environment (AWS).
- Collection: Accessing and exfiltrating data from S3 buckets and sensitive RDS databases.
- Exfiltration: Data stolen via access granted by the compromised IAM credentials.
- Impact: Data disclosure risk, potential service disruption during remediation, necessary massive credential rotation effort.
## Impact Assessment
- Financial: Not disclosed, but significant investigation and remediation costs are implied.
- Data Breach: Sensitive data likely exfiltrated from RDS databases and S3 buckets; the full scope is unknown due to log tampering.
- Operational: Initial operational disruption related to forensic analysis, EC2 instance quarantine, and subsequent investigation into the insider-like re-compromise.
- Reputational: Not disclosed, but a complex, two-year breach involving on-premises access and subsequent cloud system compromise carries high reputational risk.
## Indicators of Compromise
- Network indicators: Communication with the same IP address identified via threat intelligence analysis (IP defanged: *Attacker_IP_Address_Placeholder*).
- File indicators: Instances contained attacker-deployed reverse shells.
- Behavioral indicators: Suspicious IAM activity, specifically repeated use of the `GetPasswordData` API call against production instances just prior to reverse shell deployment; unauthorized modifications to RDS audit policies.
## Response Actions
- Containment: Quarantine of all identified compromised EC2 instances; rotation of the compromised privileged IAM user credentials (twice); rotation of *all* privileged AWS credentials.
- Eradication steps: Recovery of compromised EC2 instances from verified secure backups; restoration of tampered logging policies.
- Recovery actions: New detection rules added to the SIEM; comprehensive VPC Flow Logs configured for enhanced auditing. Final eradication required forensic analysis of the employee's personal device to remove the initial infection source.
## Lessons Learned
- The necessity of long-term, immutable logging, especially across hybrid environments (discovery was severely hindered by limited log retention in the SIEM: "only a portion was retained... for the relevant timeframe of over a year").
- Attackers can maintain persistence across significant remediation efforts (re-compromise occurred with a *new* key).
- Insider threat suspicion is a dangerous distraction; comprehensive intelligence-driven forensics tracing back to the original endpoint (home computer) is vital.
- The success of the response relied heavily on combining classic log analysis, endpoint forensics, and external threat intelligence data.
## Recommendations
- Implement comprehensive, immutable, and long-term centralized logging across both cloud and on-premises environments, ensuring audit trails are not only retained but also protected from alteration.
- Review and severely limit the use of highly privileged IAM actions like `GetPasswordData`, favoring more secure methods for bootstrapping access.
- Establish robust forensic plans covering scenarios where initial network access originates from non-corporate assets (e.g., employee home devices used for remote access).
- Automate the rotation of *all* privileged credentials immediately following any suspected compromise, even temporary ones.