Level 1 This is the highest and most stringent level of PCI DSS compliance. Level 1 is designated for merchants processing over 6 million Visa or MasterCard transactions per year. Merchants at this level are required to undergo an annual on-site review by a qualified security assessor (QSA) and to complete a formal Report on Compliance (ROC). They must also perform quarterly network scans by an Approved Scanning Vendor (ASV). Major companies like Amazon and Walmart fall into this category, necessitating robust security measures due to the volume of transactions they handle. Level 2 Level 2 merchants process between 1 million and 6 million Visa or MasterCard transactions annually. They are not required to have an on-site audit by a QSA but must complete a Self-Assessment Questionnaire (SAQ) to demonstrate compliance. Additionally, they must conduct quarterly network scans by an ASV. A company like a large regional retail chain, processing millions but not tens of millions of transactions, would typically fall into this level. Level 3 Level 3 is designated for merchants processing 20,000 to 1 million Visa or MasterCard e-commerce transactions per year. These merchants must also complete an SAQ and undergo quarterly ASV scans. This level typically includes...