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Capital One data breach: Two security controls you should review

Originally published on August 7, 2019 at

On July 19, 2019, Capital One® announced that an attacker gained access to over 100 million American and Canadian customer records containing sensitive data such as social security numbers, names, and dates of birth.

Everyone is paying a lot of attention to the fact that Capital One store the stolen data in a Capital One AWS S3 bucket. However, this attack was not specific to the AWS infrastructure and could have occurred in an on-premise deployment.

The US court complaint]( states that the breach began with a misconfiguration on a Capital One Web Application Firewall (WAF), allowing the attacker to use the WAF to attempt to access data in over 700 of the company’s S3 buckets. At least one of these S3 buckets allowed the WAF to list and extract the stolen sensitive data in a Server-Side Request Forgery (SSRF) attack. The following diagram offers a high-level overview of the attack process:

Capital One has a well-regarded security program in place, which they displayed during their incident response. Their security team maintains an email address for the responsible disclosure of vulnerabilities and incidents, which is how they identified the breach. A key lesson from this incident is that even organizations with well-run security programs are susceptible to breaches, and they must plan for such events in advance.

Onica believes that solid security fundamentals should be applied to all information technology, regardless of its physical location. After any breach announcement, we recommend that companies examine their current security practices to ensure that they are not vulnerable to the exploits. While examining this incident, we would like to focus on two security controls: misconfigurations and access rights.


Using a WAF to protect web traffic is considered a best practice. Having misconfigurations of these devices is a predictable scenario. You can mitigate Configuration error risks in multiple ways. A solid change management program in place helps minimize errors, while having a continual compliance monitoring solution in place enables you to identify misconfigurations and correct them quickly. Regularly scheduled vulnerability scans and penetration tests help identify issues that occur due to misconfigurations.

Access Rights

Creating an AWS Identity and Access Management (IAM) role intended for a WAF with access rights to one or more S3 buckets containing sensitive customer data is a major concern. While a WAF might have a legitimate reason for accessing S3 buckets (such as for logging), it is unlikely that a WAF role would require specific access to this S3 bucket considering the data it contained. This might have been an oversight in the access review process or an overall architectural issue. Onica recommends that companies examine their existing IAM roles to ensure that you follow the principle of least privilege. Follow this principle by periodically conducting an ongoing review process. Finally, putting behavioral detection technologies in place can alert you to abnormal access activities, such as a WAF role attempting to access 700 S3 buckets.

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Greg Peterson

Greg is a Lead Cloud Security Architect at Rackspace Technology.

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