PCI DSS is comprised of 12 requirements for protecting account data:

1.0: Install and maintain a firewall configuration to protect cardholder data.

2.0: Do not use vendor supplied defaults for system passwords and other security parameters.

3.0: Protect cardholder data.

4.0: Encrypt transmission of cardholder data across open, public networks.

5.0: Use and regularly update anti-virus software and programs.