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Subject: RE: Observable Patterning


What implication would patterning in STIX Indicators have for the relationship between STIX Indicators and CybOX objects?

 

In order for a pattern to be specified in a STIX Indicator (e.g., ‘IP Address in 1.2.3.4/24’), would the pattern would need to use fields from a CybOX object? If the answer is yes, does that create a hard dependency between STIX Indicator and a particular CybOX object and version?

 

What about consistency with other uses of STIX Indicator? Consider a SNORT signature or YARA rule – patterning is contained in those signatures and wouldn’t be at the STIX Indicator level, which seems inconsistent to me.

 

> Patterning should live in _one_ place and have _one_ syntax.

I really like this idea, and I’m asking questions that I hope will lead us in this direction.

 

Thank you.

-Mark

 

From: cti@lists.oasis-open.org [mailto:cti@lists.oasis-open.org] On Behalf Of Trey Darley
Sent: Thursday, September 24, 2015 4:30 AM
To: Kirillov, Ivan A. <ikirillov@mitre.org>; cti@lists.oasis-open.org
Subject: [cti] Re: Observable Patterning

 

+100, Ivan.

 

Patterning should live in _one_ place and have _one_ syntax.

 

I tend to think the STIX Indicator level is the right place for this to live.

 

Cheers,

Trey

--

Trey Darley

Senior Security Engineer

Soltra | An FS-ISAC & DTCC Company

 


From: cti@lists.oasis-open.org <cti@lists.oasis-open.org> on behalf of Kirillov, Ivan A. <ikirillov@mitre.org>
Sent: Monday, September 21, 2015 19:47
To:
cti@lists.oasis-open.org
Subject: [cti] Observable Patterning

 

Relaunching this as a separate thread based on Jerome’s suggestion, so as to not further hijack the discussion around Bernd’s suggested refactoring.

 

I think there are a few broad questions around this topic that we can touch upon here: 

 

1.

What capabilities should STIX/CybOX patterning have?

2.

Where should STIX/CybOX patterning live?

3.     Should patterns have their own implementation/structure, or continue to be embedded in Observables/Objects?

 

As far as 1) I would say the following, as a straw man:

 

* Conditional operators

    * AND

    * OR

    * NOT

* Basic temporal operators

    * FOLLOWED_BY

    * WITHIN

* String matching

    * EQUALS

    * DOES_NOT_EQUAL

    * CONTAINS

    * DOES_NOT_CONTAIN

* Basic arithmetic operators

    * >

    * <

    * >=

    * <=

* Regular Expressions

    * PCRE compatible

* Variable substitution

 

Regarding 2), it seems to me that patterning is inherent to Indicators, and thus should be part of STIX. I just can’t see the use case for a CybOX Observable with a pattern that stands on its own, or is used in a non-Indicator context. This would also serve to greatly simplify CybOX, as it would mean that CybOX can ONLY capture instances of cyber data. 

With regards to 3), I see lots of advantages to having a separate structure for patterns, which I’ve documented in the corresponding CybOX issue [1]. The short of it is that it will get rid of the instance/pattern duality, allow for the creation of a domain-specific patterning language (necessary for more complex pattern expressions), and also give us the flexibility to move patterning out to wherever makes the most sense (whether it’s STIX or somewhere else).

 

 

Regards,

Ivan



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