17
Mar
18

Can Every Requirement Be Met With A Compensating Control?

“In theory, theory works.” – Jeff Hall

Some years back, the PCI SSC came out at the Community Meeting and stated that every PCI DSS requirement could be addressed by a compensating control worksheet (CCW).  A rather broad statement but it started a bunch of us in the PCI community thinking, “Is that really the case?”

Before reading this post, I highly recommend reading my post on writing CCWs so that you can fully appreciate why not every requirement can be met by a CCW.

That said, it turns out that there are a lot of requirements where there is no way to develop a CCW.  Here are just a few examples.

1.1.2 – Network Diagram(s) and 1.1.3 – Data Flow Diagram(s)

What would be the mitigating controls here?  There are none because diagrams are diagrams.  There is nothing you can do to compensate for these missing other than provide them.

1.1.6 – Firewall Rules

As with 1.1.2 and 1.1.3, what could possibly serve as a mitigating control?  If the firewall rules are not able to be reviewed, there is nothing you can rely upon to go above and beyond the control.

I have had people suggest that the QSA could rely on Nmap and vulnerability scans of the firewalls.  But that does not necessarily confirm all of the ports/services that are configured for the firewall nor does it necessarily confirm that the devices using those ports are the same ones that are in scope for PCI compliance.

1.2.3 – Wireless Networking

QSAs have repeatedly been told that this requirement can never be marked as ‘Not Applicable’.  The QSA is required to respond to how they confirmed at wireless was either in or out of scope.  But can you create a CCW for these requirements?

The controls that you need to assess to meet these requirements are the same controls you have to use in the CCW for mitigation.  So, if you have to document and evaluate the controls regardless, why would you bother to write a CCW?  You would not.  You would document and meet the requirements and move on.

3.2 – No Storage of SAD

This is the requirement that started the whole CCW debate.  When the PCI DSS was originally issued, QSAs were trained that this requirement could NEVER, EVER have a compensating control.  But that changed when the Council issued their proclamation a few years back.  But is that really the case?

Remember, a CCW must go above and beyond the intent of the original requirement.  3.2 also states in a note that SAD cannot be stored even if encrypted.  Encryption would be the only mitigating control available to an organization that wants to store SAD.  So what replaces encryption if that cannot be used?  Tokenization by a third party would be an option, but if you go that route, you are not storing the SAD, so the discussion becomes moot.

8.3 – Multifactor Authentication

Some form of multifactor authentication (MFA) is required for non-console administrative access to cardholder data environment (CDE) systems and remote access to an in-scope network.  Since the Council has clearly defined MFA and also knocked down multiple logons with different credentials, what is left?  In the end, there is no way around meeting this requirement other than doing what the requirement states.

10.1 – 10.3 and 10.6 – Log Data

Here is another example of where there really is no way to write a CCW.  You are either gathering log data (centrally or on individual systems) or you are not.  You are either reviewing the log data daily or you are not.  Then there is the requirement of sending log data from internet facing devices to an internal device.  No matter how creative you think you are, there are no controls that will mitigate this situation and also go above and beyond.

As I said at the beginning of this post, these are just some of the examples where a CCW is just not going to make it.  So, the next time you think about meeting a PCI DSS requirement by using a CCW, make sure you understand the requirement and that there are controls that will mitigate the risk and go above and beyond the original intent of the requirement.  You will save yourself and your QSA a lot of time and consternation.

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