The Payment Card Industry Data Security Standards (PCI DSS) is a proprietary information security standard designed to ensure that companies processing, storing or transmitting payment card information maintain a secure environment. The PCI DSS applies to credit cards from the major card brands, including Visa, MasterCard, American Express, Discover, and JCB. A third-party PCI Qualified Security Assessor (QSA) assesses company systems and processes on an annual basis and issues an Attestation of Compliance (AOC).