Full Report
Researchers discovered a ransomware campaign leveraging AWS Server-Side Encryption with Customer Provided Keys (SSE-C) to encrypt data in Amazon S3 buckets. The attack, orchestrated by the threat actor "Codefinger," uses compromised AWS credentials to encrypt files securely. V...
Analysis Summary
# Incident Report: Codefinger S3 SSE-C Ransomware Campaign
## Executive Summary
A ransomware campaign orchestrated by the threat actor "Codefinger" was discovered abusing legitimate AWS Server-Side Encryption with Customer Provided Keys (SSE-C) functionality to encrypt data within Amazon S3 buckets. Attackers used potentially compromised AWS credentials with S3 operational permissions to generate unique AES-256 keys locally, encrypting data on the victim's behalf. The impact involves data inaccessibility and the imminent deletion of files, requiring ransom payment to obtain the decryption keys.
## Incident Details
- Discovery Date: January 13, 2025 (Date of Publication/Public Disclosure)
- Incident Date: Ongoing campaign (Specific onset unknown)
- Affected Organization: Undisclosed Organizations utilizing Amazon S3
- Sector: Cloud Infrastructure Users
- Geography: Undisclosed (Global impact potential)
## Timeline of Events
### Initial Access
- Date/Time: Unknown prior to Jan 13, 2025
- Vector: Compromised AWS Credentials
- Details: Threat actors acquired disclosed or stolen AWS access keys possessing permissions necessary to execute S3 operations.
### Lateral Movement
- Not explicitly detailed, but implied movement within the AWS environment to target S3 buckets is presumed using the acquired credentials.
### Data Exfiltration/Impact
- Encryption of S3 object data using AWS SSE-C.
- Placement of ransom notes in affected directories.
- Configuration of S3 lifecycle policies to schedule affected files for deletion within seven days to increase pressure.
### Detection & Response
- Detection Method: Security researchers identified and publicized the campaign methodology.
- Response Actions: Not detailed within the context, but focus shifts to containment and recovery post-discovery.
## Attack Methodology
- Initial Access: Acquisition of compromised AWS access keys (disclosed or stolen).
- Persistence: Not explicitly detailed, but access maintained via valid credentials.
- Privilege Escalation: Not explicitly detailed.
- Defense Evasion: Utilizing legitimate AWS services (SSE-C) prevents detection via traditional signature-based methods as no malicious file drops occur on compute instances.
- Credential Access: Exploitation of already compromised or leaked AWS credentials.
- Discovery: Utilizing valid credentials to enumerate and target S3 buckets.
- Lateral Movement: Movement across AWS resources permitted by the acquired credentials.
- Collection: Data identification within S3 buckets.
- Exfiltration: Data is *not* traditionally exfiltrated; rather, access is revoked via encryption.
- Impact: Data rendering inaccessible via encryption using locally generated keys, with a strict time limit (7 days) before permanent deletion.
## Impact Assessment
- Financial: Ransom payment required for decryption keys. Potential costs associated with rebuilding or recovery efforts.
- Data Breach: Data remains resident in S3 but is encrypted and inaccessible; decryption keys are held by the threat actor.
- Operational: Critical operational data stored in S3 becomes unusable until the ransom is paid or recovery methods are implemented.
- Reputational: Potential reputational damage associated with cloud security posture failures and data loss incidents.
## Indicators of Compromise
- Network Indicators: Not specified (rely on standard AWS API call monitoring).
- File Indicators: Ransom notes placed in S3 directories.
- Behavioral Indicators: High volume of S3 `PutObject` operations utilizing the `x-amz-server-side-encryption-customer-key-MD5` header during encryption, alongside the creation of S3 Lifecycle rules targeting expiration within ~7 days.
## Response Actions
*Note: Responses are speculative based on the nature of the attack as specific actions were not provided.*
- Containment measures: Immediate revocation and rotation of all potentially compromised AWS credentials discovered to be associated with the targeting activity.
- Eradication steps: Removal of S3 lifecycle policies set by the attacker to prevent file deletion.
- Recovery actions: Restoration of data from backups taken *prior* to the S3 encryption event, or engaging with the attacker if no viable backups exist (based on threat actor discretion).
## Lessons Learned
- Utilizing native, legitimate platform features (like SSE-C) can be abused by attackers to achieve impact without triggering traditional security alerts focused on malware or configuration drift.
- The primary weakness exploited was the compromise of the credentials necessary to initiate these critical S3 operations.
- AWS only retains an HMAC of the SSE-C key; therefore, the only viable path to recovery may rely directly on the attacker.
## Recommendations
- **Credential Management:** Implement strict access controls (IAM policies) limiting S3 operational permissions to only necessary users/roles. Employ MFA universally and utilize temporary credentials (STS) whenever possible.
- **Monitoring:** Enhance monitoring for unusual S3 API activity, specifically targeted uploads utilizing SSE-C, and the creation or modification of S3 Lifecycle Management policies by non-standard principals.
- **Backup Strategy:** Ensure robust, immutable backups of critical S3 data are maintained geographically or logically separate from the primary production environment, ideally without utilizing the same credentials pipeline as the primary S3 environment.