This is a guest post by Anton Chuvakin (RSS), co author on our PCI Compliance book.  Follow him on Twitter at @Anton_Chuvakin.

People who came to PCI DSS assessments and related services (such as compliance gap analysis and even implementation of PCI controls) from doing pure information security often view scope reduction as “a cheap trick” aimed at making PCI compliance undeservedly easier. They only think of scope reduction as of limiting the area where PCI DSS security controls apply—with negligence, supposedly, reigning supreme outside of that sacred area.

Welsh Landscape, by Richard0

However, PCI DSS scope shrink is not just a cop out aimed at not protecting data. It is not just a “PCI project cost reduction” measure. Some half-witted analysts propagate this view by saying things like “by reducing the scope, these enterprises can dramatically lower the cost and anxiety of PCI DSS compliance and significantly increase the chance of audit success” [eh… for starters, PCI on-site assessment is not an audit, stop calling it that!] Well, you will get that—but it is not the point of scope reduction at all.

In reality, efforts to reduce the area of PCI DSS applicability—scope reduction—are one of the most effective ways to reduce the risk of cardholder data theft.

Like we say in our PCI book (Chapter 5, “Protecting Cardholder Data”):

Before we even start our discussion of data protection methods, we need to remind you that “the only good data is dead data.” Humor aside, dropping, deleting, not storing and otherwise not touching the data is the best single trick to make your PCI DSS compliance easier as well as to make the transaction less risky, reduce your liability, chance of fines and breach notification losses.

If you’d like, think of scope reduction as one of the manifestation of the “least privilege” principle—or least data needed to do business principle. You stop the spread of card data and thus become a more compact, harder to hit target.

Along the same line, tokenization, data vaults, virtual terminals, hashing, network segmentation, and transient PAN storage all reduce scope and risk at the same time. These are the things that make PCI compliance easier WHILE reducing the risk of damaging compromise. So, reduce scope by changing business process—it will bring more security benefits than THAT FIREWALL you deploy.

And remember that fable about a QSA firm that wanted to accept payment cards as payment for assessments (oh irony!): “… we don’t touch that toxic [card data] shit!”

Now that you’ve read Anton’s post, go check out my post on his blog!

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