I was just walking one of my clients through a PayPal Pro signup and noticed that PayPal has partnered with Scanalert to provide free service for a year.
here is the direct link that PayPal gives you for the free deal
I would love to know if Magento passes these tests. I understand that a lot of it has to do with your hosting environment, but a lot of it has to do with code too. And since the scans are free, I think the Magento team should take advantage.