An SLA Starter For PCI Compliance In The Cloud

A 403 Labs QSA, PCI Columnist Walt Conway has worked in payments and technology for more than 30 years, 10 of them with Visa.

With the boost in momentum from cloud efforts—and the emergence of PCI-compliant cloud service providers (CSPs)—there is an immediate need to radically rethink what elements need to go into your service level agreements (SLAs) with those Cumulus providers. Consider: If the CSP is responsible for installing vendor security patches (Requirement 6.1), how will you verify that they test the patches first, to make sure they won't break your application, and then install them promptly?

As a QSA, I'd pay particular attention to patches the vendor identifies as critical, because those have to be installed within 30 days. Will you be able to see a log or other evidence that the patches were installed on all in-scope systems? Another example is your internal and external vulnerability scans. You need to have the CSP provide reporting each quarter on both your complete internal vulnerability scans and your external scans, which an ASV must perform. Another example is the physical security of the vendor's facility. Can you inspect it to see that the badging, video recordings and visitor logs are all maintained? Because it is quite possible that a cloud provider will have offshore datacenters, what is its plan for you to validate those centers are performing as expected? A brochure might be pretty, but it is not verification of performance.

Let's start with one basic premise: Using a PCI-compliant CSP is no guarantee that you, the customer (i.e., the merchant), are yourself compliant. The cloud is no more of a silver bullet than any other PCI-compliant service provider or implementing a PA-DSS validated application. What you are buying is an opportunity to make your compliance easier, faster and, maybe, cheaper. What you want to avoid is making compliance more complicated, slower and, maybe, more expensive. A merchant does not "catch" PCI compliance from its CSP—even a PCI-compliant one—like you catch a cold on the subway.

To my way of thinking, a merchant needs to start with a spreadsheet that lists each PCI requirement in one column (and yes, I mean all 240+ requirements). The next spreadsheet column details who is responsible for that requirement, with the options being: the CSP, the merchant or shared. You cannot even begin a serious discussion without this spreadsheet.

Start with those items that are marked "merchant." Can your organization handle its share of the responsibility for compliance? Will the CSP's solution reduce the compliance effort and cost sufficiently to justify the expense? As the merchant, do you have the resources to take on the specified responsibilities and manage the cloud provider?

This is also the time to be clear with your CSP about any critical, deal-breaking elements. For example, data privacy or other regulations may dictate that personal data such as payment cards never leave a certain jurisdiction. In these cases, the cloud provider will not be able to move your data between its datacenters in different countries as it pleases. So if you cannot have your data bouncing from the U.S. to Singapore to England to wherever, make it clear upfront.

Next, let's move to the "CSP" and "joint" requirements. Even though a requirement is marked as being the cloud provider's responsibility, that does not let the merchant off the PCI hook. I would want to examine the executive summary of the CSP's Report on Compliance (ROC) to confirm that the PCI assessment covered the scope of services the merchant is buying. Remember, your cloud provider is like any other service provider: You can outsource the processing, but you cannot outsource the responsibility.

Therefore, I'd like now to introduce a third column to our spreadsheet that will further inform our SLA.Therefore, I'd like now to introduce a third column to our spreadsheet that will further inform our SLA. That column has the details on how you will validate the CSP is indeed meeting that particular requirement every day of the year.

I have trouble understanding how any CSP will help a merchant meet some particular PCI requirements. The example that comes to mind is the requirement for daily log review (10.6). I wonder how a merchant can reasonably outsource that requirement or even why it would want to. A multi-tenant cloud compounds the problem, because the vendor's logs will have information on the other organizations sharing the cloud. In this case, the vendor will understandably be reluctant to share the logs, but PCI requires it. I still haven't completely figured that one out.

I cannot see how any CSP can be expected to monitor your logs effectively. The reason is the provider has no context to evaluate the alerts. For example, how can a CSP know to red flag an admin logging in at 3 A.M. when only you know that person is on vacation?

Substitute "File Integrity Monitoring" (Requirements 11.5 and 10.5.5) for "daily log review" in the above paragraphs, and you have another awkward situation. And in no situation that I can imagine will a merchant be able to outsource its security policies (Requirement 12)—in particular, incident response planning. More likely, the CSP and the customer will need to coordinate their respective response plans to reconcile differences in policy, procedure, disclosure, legal issues and forensics. I would not underestimate the importance of coordinating incident response planning, given the extreme sensitivity of any data breach.

If I were a merchant looking at a cloud vendor, I would not be afraid to ask a lot of questions and make a lot of demands. At the recent RSA Conference, I heard one prominent CSP tell an audience of potential customers that they (the audience) needed to start making tougher demands and asking hard questions of their cloud providers. Otherwise, his company and others would never provide the necessary functions and services. That was a refreshing bit of honesty that too many people in the audience may not have heard. If so, that's too bad, because I agree with that speaker.

Another person I spoke with at RSA was Bob Russo, General Manager of the PCI Security Standards Council. I asked him if he thought PCI DSS was ready for cloud computing. He thoughtfully turned the question back at me. He said that PCI as a standard was definitely ready for the cloud, but the better question might be: Is the cloud ready for PCI?

That is a good question, and one that many potential cloud customers and their QSAs will be asking, too. The emergence of PCI-compliant cloud providers is a positive sign. But it is not a free ride on PCI requirements. Even in the most full service of SaaS clouds a merchant will have some PCI responsibilities. If nothing else, there will be Requirement 12.

Merchants using clouds of all flavors will need to validate that their cloud provider performs per their contract and PCI requirements. Simply taking the cloud provider's Attestation of Compliance and checking the "yes" box on all the PCI requirements will not cut it with too many QSAs. Like I've said many times, PCI has outlawed silver bullets.

What do you think? Are you considering a cloud-based payment solution? I'd like to hear your thoughts and experiences. Either leave a comment or E-mail me at [email protected].