Throughput* is perhaps the wrong unit of measure. Most of the time you would be interested in measuring “requests/second” or “transactions/second”. Aside from say a content ingesting site/repeater (facebook/twitter/instagram), almost all content for a WAF to handle is inbound, using low amounts of available bandwidth. The outbound content is rarely inspected by such a device, with the exception of 5xx error or similar (headers).

A colleague pointed out you are missing the fact that if the WAF is oversubscribed, you will miss attacks. They are related to the other sets of metrics, dependent on the level of performance you desire. However, it is important to score them in isolation as well, since you need to understand the value of protection outside the scope of resource contention. Typically we would encourage users to set the performance targets they expect, and then test the protection capabilities of said solution, be it intrusion prevention, WAF, firewall state tracking, whatever. Then iteratively increase said performance testing until the device would reach a failure point in terms of performance or security protection objectives.

-chuck

* throughput has a technical definition of “the fastest rate at which the count of test frames transmitted by the DUT is equal to the number of test frames sent to it by the test equipment.” (RFC 2544). It’s used for switches and routers. No one cares anymore, but hey, I hold a torch for it. The term “goodput” is stuff meat of what you care about (webpages, documents, whatever).

From: Dave Aitel via Dailydave dailydave@lists.aitelfoundation.org Reply-To: Dave Aitel dave.aitel@gmail.com Date: Tuesday, January 5, 2021 at 9:46 AM To: "dailydave@lists.aitelfoundation.org" dailydave@lists.aitelfoundation.org Subject: [Dailydave] The Lost Decade of Security Metrics

[EXTERNAL] A thousand years ago I subscribed to the Security Metrics mailing list. Metrics are important - or rather, I think good decision making is important, and without metrics your decision making is essentially luck. But we haven't seen any progress on this in a decade, and I wanted to talk about the meta-reason why: Oversimplification in the hopes of scaling.

There's a theme in security metrics, a deep Wrong, that the community cannot correct, of trying to devolve features in their datasets to a single number. CVSS is the most obvious example, but Sasha's VEP paper here (https://www.lawfareblog.com/developing-objective-repeatable-scoring-system-v...https://urldefense.com/v3/__https:/www.lawfareblog.com/developing-objective-repeatable-scoring-system-vulnerability-equities-process__;!!I5pVk4LIGAfnvw!1_DCQdbQK-EjdSvoz7gu1f7ZwUzSyy8xrv6jrZQI1ZbraPepIeNytbPZ-yN5YZ8c$) demonstrates most clearly the categorical example of the oversimplification issue, one that all of FIRST has seemingly fallen into.

If I took all the paintings in the world, and ran them through a neural network to score them 1.0 through 10.0, the resulting number would be, like CVSS, useless. Right now on the Metrics mailing list someone is soliciting for a survey where they ask people how they are using CVSS and how useful it might be for them. But the more useful you think CVSS is for you, the less useful it actually is being, since it can only lead you to wasting the little security budget you have. CVSS is the phrenology of security metrics. Being simple and easy to use does not make it helpful for rational decision making.

If we want to make progress, we have to admit that we cannot join the false-positive and false-negative and throughput numbers of our WAF in any way. They must remain three different numbers. We can perhaps work on visualizing or representing this information differently, but they're in different dimensions and cannot be combined. The same is true for vulnerabilities. The reason security managers are reaching for a yes/no "Is there an exploit available" metric for patch prioritization is that CVSS does not work, and won't ever work, and despite the sunk cost the community has put into it, should be thrown out wholesale.

-dave

I don't think you are wrong but your comparison of CVSS and the multiple (also separately bad) metrics for a WAF isn't effective or accurate.

The values going into CVSS have something in common; they are attempts to characterize the importance of the vulnerability in question. You are making (have made before) the claim that the importance of a vulnerability is too variable and specific to an environment or an attack scenario to be effectively captured with the values included in CVSS.

In contrast, WAF throughput, false positives, and false negatives are tradeoffs. They are equivalent to "cheap, fast, good; choose two". The whole point of this set of values is that they can't be combined and as far as I know, no one is trying to combine them at present. Neohapsis was the last (qualified, thoughtful) group to try to actually produce scores for IDS and Firewalls and I believe that died over drinks in Portland many many years ago. No one deploying a WAF combines those. They use them to talk about prioritization and risk tolerance. Is it better to impact performance, risk false negatives, or suffer false positives? That's a choice made by each company.

The equivalent of the WAF values for a vulnerability might be "importance of the vuln", "confidence in the fix mitigating the vuln", "risk of the fix breaking your environment". Or something like that.

The question is; do companies need CVSS to be better? Or is it sufficient when used as a tool to think about vulnerabilities?

I'd suggest that you are more focused on the nuances of vulnerabilities than most companies have time or desire to be. That makes sense given what you've spent your career so far doing. But if you want to change how things are done you can't insist that everyone step up to your level of knowledge & focus. So, how do you create a repeatable process that can be adopted and adapted to each company that uses it without requiring someone who has spent 20 years deeply thinking about exploitation to do the analysis of each new vuln?

t

On Tue, Jan 5, 2021 at 6:50 AM Dave Aitel via Dailydave < dailydave@lists.aitelfoundation.org> wrote:

A thousand years ago I subscribed to the Security Metrics mailing list. Metrics are important - or rather, I think good decision making is important, and without metrics your decision making is essentially luck. But we haven't seen any progress on this in a decade, and I wanted to talk about the meta-reason why: Oversimplification in the hopes of scaling.

There's a theme in security metrics, a deep Wrong, that the community cannot correct, of trying to devolve features in their datasets to a single number. CVSS is the most obvious example, but Sasha's VEP paper here ( https://www.lawfareblog.com/developing-objective-repeatable-scoring-system-v...) demonstrates most clearly the categorical example of the oversimplification issue, one that all of FIRST has seemingly fallen into.

If I took all the paintings in the world, and ran them through a neural network to score them 1.0 through 10.0, the resulting number would be, like CVSS, useless. Right now on the Metrics mailing list someone is soliciting for a survey where they ask people how they are using CVSS and how useful it might be for them. But the more useful you think CVSS is for you, the less useful it actually is being, since it can only lead you to wasting the little security budget you have. *CVSS is the phrenology of security metrics.* Being simple and easy to use does not make it helpful for rational decision making.

If we want to make progress, we have to admit that we cannot join the false-positive and false-negative and throughput numbers of our WAF in any way. They must remain three different numbers. We can perhaps work on visualizing or representing this information differently, but they're in different dimensions and cannot be combined. The same is true for vulnerabilities. The reason security managers are reaching for a yes/no "Is there an exploit available" metric for patch prioritization is that CVSS does not work, and won't ever work, and despite the sunk cost the community has put into it, should be thrown out wholesale.

-dave _______________________________________________ Dailydave mailing list -- dailydave@lists.aitelfoundation.org To unsubscribe send an email to dailydave-leave@lists.aitelfoundation.org