Whether paying by VISA, Mastercard or PayPal, PayPal handles all of our processing. From the PayPal website:
The PayPal site is highly secure. We use industry-leading technology (such as SSL) to keep your information safe.
PayPal automatically encrypts your confidential information in transit from your computer to ours using the Secure Sockets Layer protocol (SSL) with an encryption key length of 128-bits (the highest level commercially available). Before you even register or log in to the PayPal site, our server checks that you're using an approved browser - one that uses SSL 3.0 or higher.
Once your information reaches the PayPal site, it resides on a server that is heavily guarded both physically and electronically. PayPal servers sit behind an electronic firewall and are not directly connected to the internet, so your private information is available only to authorized computers.