You must have the right security in place to protect data against theft when selling online. Being PCI DSS (Payment Card Industry Data Security Standard) compliant means card details from your customers are protected when they shop with your online store.
One of the big benefits of using an ecommerce website builder is that security is usually bundled up with your subscription. Most builders provide a free SSL certificate, and others, like Shopify, offer fraud detection to monitor purchases for you.