A new wave of cloud ransomware – most notably the campaign dubbed Codefinger – is targeting Amazon S3 buckets by commandeering native AWS encryption features. This emerging threat signals a serious escalation: attackers are now leveraging legitimate cloud infrastructure to hold data hostage.

What Has Changed?

• SSE‑C being weaponised
  Attackers obtain compromised AWS credentials that allow s3:GetObject and s3:PutObject. Then they encrypt objects using Server-Side Encryption with Customer‑Provided Keys (SSE‑C) – keys known only to the attacker, rendering data unrecoverable.
• Time-bomb deletion strategies
  Encrypted objects are scheduled for deletion via S3 lifecycle policies – often within seven days – coercing victims to pay promptly.
• “Silent” encryption
  As AWS logs only an HMAC of the encryption key – not the key itself – victims and AWS struggle to detect or reverse the attack.

Why This Can’t Be Ignored

• Legitimate tools turned malicious
  Rather than exploiting AWS code, attackers rely solely on stolen credentials – no AWS vulnerabilities are required.
• Common IAM misconfigurations
  Many AWS environments grant overly permissive access; in some organisations, compromised credentials provided ransomware capability across most or all S3 buckets.
• Low visibility, high impact
  As no data is exfiltrated and the bucket structure appears intact, the attack may go unnoticed until it’s too late.

How to Shield Your Buckets

Control Area	Mitigation Measures
IAM permissions	Minimise privileges – deny SSE‑C unless explicitly required; prefer IAM roles over long-term access keys
Encryption strategy	Disable SSE‑C where possible; favour AWS‑managed keys (SSE‑S3 or SSE‑KMS) that AWS controls
Monitoring & logging	Enable S3 data‑event logging in CloudTrail; deploy tools like AWS GuardDuty and YES3 Scanner to detect anomalies
Backup & recovery	Enable versioning and Object Lock; maintain immutable, offline backups to mitigate timed deletions
Credential hygiene	Rotate or disable stale access keys; enforce multi‑factor authentication (MFA) for IAM users
Education & awareness	Ensure engineers avoid embedding credentials in code and follow secure storage practices

Turning Risk into Resilience

This shift in tactics represents a broader trend: cloud infrastructure features are now tools for attackers as much as defenders. Relying on AWS’s built‑in protections alone is no longer sufficient. Security teams must assume compromise and build resilience – precise IAM policies, robust log analysis, and tested recovery protocols form the new frontline.

Partner with Vertex Agility for Cloud Security

At Vertex Agility, we provide agile, on‑demand tech teams equipped to shore up your cloud defences swiftly. From tightening IAM policies and disabling exploitable encryption options to implementing immutable backups, monitoring systems, and incident response playbooks – we help you reclaim control of your cloud environment. Don’t wait for the next ransomware wave to hit. Contact us to build the expert capability you need, exactly when you need it.