Re: The Lost Decade of Security Metrics

[Chuck McAuley via Dailydave <dailydave () lists aitelfoundation org>]

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-vulnerability-equities-process<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

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