https://www.pcisecuritystandards.org/pci_security/maintaining_payment_security

Build and Maintain a Secure Network

1. Install and maintain a firewall configuration to protect cardholder data.

2. Do not use vendor-supplied defaults for system passwords and other security parameters.

Protect Cardholder Data

3. Protect stored cardholder data.

4. Encrypt transmission of cardholder data across open, public networks.

Maintain a Vulnerability Management Program

5. Use and regularly update anti-virus software or programs.

6. Develop and maintain secure systems and applications.

Implement Strong Access Control Measures

7. Restrict access to cardholder data by business need-to-know.

8. Assign a unique ID to each person with computer access.

9. Restrict physical access to cardholder data.

Regularly Monitor and Test Networks

10. Track and monitor all access to network resources and cardholder data.

11. Regularly test security systems and processes.

Maintain an Information Security Policy

12. Maintain a policy that addresses information security for employees and contractors.