If your business stores, processes, or transmits credit cardholder data, you need to attain PCI compliance. For this to happen, you have to employ the services of a QSA.
Taking it straight from the horse's mouth, the horse in this case being the Payment Card Industry Security Standards Council (PCI SSC), which oversees PCI compliance:
"Qualified Security Assessor (QSA) companies are independent security organizations that have been qualified by the PCI Security Standards Council to validate an entity’s adherence to PCI DSS."
The PCI DSS (Payment Card Industry Data Security Standard) comprises 12 Requirements, some or all of which need to be met by a business / organisation to attain PCI compliance.
Some of these Requirements include:
- Encrypt transmission of cardholder data across open, public networks
- Develop and maintain secure systems and applications
- Track and monitor all access to network resources and cardholder data
QSAs themselves need to meet set criteria outlined by the PCI SSC to not only become certified, but maintain certification on a yearly basis, in order to test an entity's ability to comply with the PCI DSS.
There are just under 400 QSAs around the world, so it's no easy task becoming one. And rightly so. Credit card data is, without sounding flippant, a licence to print money.
A list of QSAs can be found on the PCI SSC website.