Amazon Elastic File System (EFS) is a serverless file system that does not require provisioning or managing storage. Stored files can be automatically encrypted by the service. In the case that adversaries gain physical access to the storage medium or otherwise leak a message they are not able to access the data.

Ask Yourself Whether

• The file system contains sensitive data that could cause harm when leaked.
• There are compliance requirements for the service to store data encrypted.

There is a risk if you answered yes to any of those questions.

Recommended Secure Coding Practices

It’s recommended to encrypt EFS file systems that contain sensitive information. Encryption and decryption are handled transparently by EFS, so no further modifications to the application are necessary.

Sensitive Code Example

For AWS::EFS::FileSystem:

AWSTemplateFormatVersion: '2010-09-09'
Resources:
  Fs:  # Sensitive, encryption disabled by default
    Type: AWS::EFS::FileSystem

Compliant Solution

For AWS::EFS::FileSystem:

AWSTemplateFormatVersion: '2010-09-09'
Resources:
  Fs:
    Type: AWS::EFS::FileSystem
    Properties:
      Encrypted: true

See

• Data encryption in Amazon EFS
• OWASP Top 10 2017 Category A3 - Sensitive Data Exposure
• OWASP Top 10 2017 Category A6 - Security Misconfiguration
• MITRE, CWE-311 - Missing Encryption of Sensitive Data