Cloud Egress Bypass and Public Bucket Exposure
Helio Commerce runs four AWS accounts and two Azure subscriptions. Its security team standardized egress inspection through a pair of FortiGate VMs in an inspection VPC, reachable via a transit gateway. Eighteen VPCs are connected, but six application teams built their own NAT gateways and internet gateways for cost and latency. FortiCNP reports 22 public S3 buckets; one contains 12,000 customer order records and is flagged for public read. A security group in the production VPC allows 0.0.0.0/0 to TCP 3389, but the attached instance is stopped. The cloud team wants to auto-remediate every critical finding and close all public buckets by Friday. The application owner says the flagged bucket serves marketing images and must stay public. Logs show 14 GET requests from an unknown IP range in the last 24 hours.
1. Prioritize the three findings and determine actual exposure before remediation.
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Rank by exploitability and data sensitivity, not by scanner severity. The S3 bucket is highest if it is truly public and contains customer order records: verify Block Public Access at account and bucket level, bucket policy, ACLs, and object-level permissions; then check CloudTrail data events for the 14 GETs and whether any object containing PII was read. Marketing images in the same bucket do not justify public read for order records; split them. The RDP security group is latent because the instance is stopped, but it becomes critical the moment someone starts it; check for other ENIs, launch templates, and auto-scaling groups using it. The egress bypass is a systemic control failure: six VPCs can reach the internet without inspection, so any future incident there is blind. Fix the bucket exposure first, then the RDP rule, then the egress architecture.
2. How do you close the egress bypass without breaking the six application teams?
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Use the transit gateway route tables to steer all VPC default routes to the inspection VPC, remove or deny the spoke NAT gateways and internet gateways, and centralize NAT behind the FortiGate VMs. That changes cost allocation and latency, so phase it: start with production and regulated VPCs, measure latency to the top five apps, and give teams a documented exception process with compensating controls. Enforce with AWS Organizations SCPs that deny IGW creation outside the network account, plus IaC policies that fail a pull request creating a local NAT. FortiGate autoscaling and health checks must be sized for the added throughput. Do not simply delete the six teams' gateways in one change; you will cause outages and lose cooperation.
3. What should be auto-remediated, and what requires human approval, in the cloud remediation policy?
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Automate containment, not destructive change. Safe auto-remediation: enable S3 Block Public Access on buckets tagged with customer data, remove security-group rules open to 0.0.0.0/0 on management ports when the resource has no approved exception tag, and enable encryption or logging. Require human approval for deleting buckets, changing application routing, or shutting down instances. For the marketing bucket, create a separate public bucket fronted by CloudFront with origin access control, migrate only static assets, and keep PII out. Preserve logs before remediation. Publish the policy so developers know what will be auto-fixed, and add a post-remediation verification step in FortiCNP.