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[Bernd Grobauer]

Hi, stepping back from the choice of binding for a moment, I would like to explore a bit, how much the next major version of STIX might differ from what we have today in terms of simplification. So, as an experiment, below I will go through the 'Indicator' entity and propose changes. Here I will try to take the side of "as simple as simple can be", be the "simpleton's" advocate, so to speak, in the hope of getting some discussion going regarding what is maybe too simplistic vs what kind of complexity we might be able to throw over board. Here is the overview of the indicator entity/concept taken from page 13 of https://github.com/STIXProject/specifications/blob/master/documents/pdf%20versions/STIX_Indicator_Draft.pdf Let me propose the following simplifications: - version:   Keep. - negate:   Remove -- the use case is mostly academic, but if the   flag is there, it completely changes the semantics of how   the indicator is to be handled and is a real pain for implementation,   even though it is hardly ever used   (Note: as shall be explained below, the 'negate' will not be needed anymore    for building logical expressions of indicators, because we shall throw those    out, too). - Title:   Make the field mandatory, but it may be empty. - Type:   Remove, if there isn't someone who can come up with a   convincing case in which the field is really useful and where   the intended semantics could not be communicated with   a reference to a COA. - Alternative_ID:   Unsure, probably keep. - Description:   - There should be exactly 1 description field (which may be empty).     Yes, this precludes fancy schemes of having different descriptions     for different audiences/access levels, but those should amount     to less than 0.1% of all indicator objects ever to be     produced and thus do not warrant substantial complication of     the standard.   - There should be exactly one text representation, and that should *NOT*     be html on account of security issues with rendering HTML in the     browser. Chose Markdown, RestructuredText or whatever. - Short_Description:   Remove: I am tired of receiving indicator objects in which   two or three out of three of the fields "title",   "description", "short_description"   are empty -- one description field should be plenty.   (Besides: everybody keeps telling me that STIX is for   machine-2-machine rather than *-2-human communication, so   why the big fuss about description fields?) - Valid_Time_Proposition:   Timing info for indicators is badly needed, but I have yet to encounter usage   of it. Can we come up with sensible guidelines of how to use the field?   It should only be kept if we can... - IndicatorExpression   In the present specification, this field can either   contain what is essentially a logical formula (codified as a tree)   of indicators or an observable composition.   - Remove logical operations: allow only to reference a list     of indicators that constitute the present indicator.   - If you want to do complicated and/or/not-reasoning about     observable stuff: that is essentially a signature,     so find a signature-language of your choice (including     and/or/not-combinations of CybOX observables, if that     is what works best) and formulate the signature     as a test mechanism.   - For everything else: find a way to encode observable     patterns as simple key-value pairs and include/reference a list     of them here. Should work fine for the majority of     current use-cases. At most, allow a structured list that     groups basic observable patterns (key-value) pairs with     respect to a cybox observable to which they belong. - Indicated_TTP:   Use yet-to-be-designed relationship mechanism. - Kill_Chain_Phases:   Define *ONE* standard STIX kill chain and work with that.   Being able to include alternative models is nice, but   complicates tooling quite a bit ... and, remember, this   is an exchange format, so one common kill-chain model   understood in the same way by everybody will work best. - Test Mechanisms   Make this a stand-alone entity/object rather than part   of the Indicator object. As mentioned above: use this also   to communicate more complicate observable patterns expressed in CybOX. - Likely_Impact.   Remove: I have never encountered it being used and have   a hard time coming up with a convincing use case. - Suggested_COAs:   Use yet-to-be-designed relationship mechanism. - Handling:   Replace with some new mechanism for marking stuff with   handling information. - Confidence   Keep: we need a simple way to distinguish high-confidence   from low-confidence indicators. - Sightings:   Find some other way to do sightings (cf. the discussion on   the mailing list) - Related_*: Use yet-to-be-designed relationship mechanism. - Producer:   Either simplify drastically or better yet, leave away   and consider for the next but one major release. Like I said above: this as an experiment of being very simple indeed (though my mind is probably too convoluted with all things CTI to come up with the super-simple thing). I am sure some of it is too simple, but with the current version of STIX we have already one extreme of complexity -- to map out our design space, we need to get a feeling for the other extreme as well, I think. Kind regards, Bernd -------- Bernd Grobauer, Siemens CERT