AWS Time Sync & PCI DSS Compliance

TL;DR

AWS Time Sync can contribute to PCI DSS compliance, specifically requirement 8 (Time Synchronization), but it’s not a complete solution. You need to configure it correctly and combine it with other security measures. This guide explains how.

Understanding PCI DSS Requirement 8

PCI DSS Requirement 8 focuses on accurate time synchronization across all system components. This is vital for effective log correlation, incident investigation, and non-repudiation. The requirement states systems must be synchronised to a reliable time source.

How AWS Time Sync Works

AWS Time Sync uses Network Time Protocol (NTP) to synchronize the clocks of your EC2 instances, ECS containers, Lambda functions, and other services with accurate time sources. It’s built into Amazon Linux 2 and later, and can be enabled on other operating systems.

Steps to Use AWS Time Sync for PCI DSS Compliance

1. Enable AWS Time Sync: For Amazon Linux 2 or later, it’s usually enabled by default. Verify using:

   timedatectl status

   Look for ‘NTP synchronized’ to be ‘yes’. If not, install and start the service (refer to AWS documentation).

2. Configure Time Sync on Other OS: For other operating systems (e.g., Windows, RHEL), you’ll need to manually configure an NTP client to use a reliable time source.
   • Choose a Reliable Time Source: Use the AWS Time Stream servers provided by AWS:

     pool.ntp.org

     or regional specific servers (e.g., europe.pool.ntp.org). Avoid using public NTP servers as they may be unreliable or compromised.

   • Install and Configure NTP: Install an NTP client like chrony or ntpd and configure it to use the AWS Time Stream servers.

     sudo yum install chrony -y # Example for RHEL/CentOS

     Edit the configuration file (e.g., /etc/chrony.conf) to include:

     server pool.ntp.org iburst

3. Monitor Time Synchronization: Regularly monitor your systems to ensure they remain synchronized.
   • Use CloudWatch Metrics: AWS Time Sync publishes metrics to CloudWatch, including ‘NTP Offset’ and ‘NTP Jitter’. Set up alarms if these values exceed acceptable thresholds (typically a few milliseconds).
   • Check Logs: Review system logs for NTP-related errors or warnings.
4. Secure Your NTP Configuration: Protect your NTP configuration from tampering.
   • Restrict Access: Limit access to the NTP service to authorized systems only using firewall rules and host-based firewalls.
   • Authentication (Optional): Consider using authenticated NTP if supported by your operating system for added security.
5. Log Correlation & Analysis: Ensure all logs across your PCI DSS environment are synchronized to the same time source.
   • Centralized Logging: Use a centralized logging solution (e.g., AWS CloudWatch Logs, Splunk) to collect and analyze logs from all systems.
   • Time Zone Consistency: Maintain consistent time zones across all components. UTC is recommended.

Important Considerations

• AWS Time Sync Alone Isn’t Enough: PCI DSS requires a comprehensive security approach. AWS Time Sync addresses only one aspect of Requirement 8.
• Regular Audits: Conduct regular audits to verify the effectiveness of your time synchronization configuration and other security controls.
• Documentation: Document your time synchronization process, including the chosen time sources, monitoring procedures, and any exceptions.