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Subject: Re: [cti] Playing the "simpleton's advocate": how much complexity can we throw overboard?


On these two points. It hard to understate how often this kind of 'complexity' is required to describe things correctly.  I know in the early days of sharing CTI via CSV files it was very common to have data that while was correct lacked the conditions to be accurately used as CTI due to the lack of structure and sequence of events.  Here is a very simple example. 


 Lets say you are doing analysis on malware and find that the infection starts uses a dropper hosted at evil2015.com and when the malware successfully installs on a victim host its checks to see if it in Internet accessible location by reaching out to innocuous domain like say www.google.com or download.microsoft.com. So if you loose the sequence here and just query all your proxy logs for all three of the domains you will get tons of results that are useless, but not wrong.  If the CTI data was instrumented to say evil2015.com and then one of these two from the same host shortly there after is a high probability of an infected machine.  You don't know that from just having a host reach the evil2015.com domain.


Including these these the innocuous domains in the CTI data is useful for both the COA side but also developing TTPs of Threat Actors as some pick particular hosts to validate Internet access and it is more valid indicative data about who might be on the far end of the keyboard.  (Yes it is not any where enough, but bread crumb trails are that way...)


Mark Clancy
Chief Executive Officer
SOLTRA | An FS-ISAC and DTCC Company
+1.813.470.2400 office | +1.610.659.6671 US mobile |  +44 7823 626 535  UK mobile
mclancy@soltra.com | soltra.com
 
One organization's incident becomes everyone's defense.
 



From: cti@lists.oasis-open.org <cti@lists.oasis-open.org> on behalf of Jason Keirstead <Jason.Keirstead@ca.ibm.com>
Sent: Monday, September 21, 2015 11:29 AM
To: Grobauer, Bernd
Cc: cti@lists.oasis-open.org
Subject: Re: [cti] Playing the "simpleton's advocate": how much complexity can we throw overboard?
 

I agree with most parts of this, but not all.

Specifically, Observable Composition and Negate are both absolutely required. In fact, they need to be further enhanced to support Sequences ( see discussion here https://github.com/STIXProject/schemas/issues/329 ).

We already have actual, real world, in the wild, threat use cases that can not be expressed in STIX today due to lack of sequences. Removing expressions and negation, will make it this situation worse, not better.

If it's agreed to move all of this logic into CybOX and do it there... then OK (CybOX will need several enhancements), but we need to retain (and enhance) the capacity of STIX here. If there are classes of cyber-onservables that can't be expressed in STIX due to simple lack of expressiveness, then it will severely limit adoption of it by tools.


-
Jason Keirstead
Product Architect, Security Intelligence, IBM Security Systems
www.ibm.com/security | www.securityintelligence.com

Without data, all you are is just another person with an opinion - Unknown


Inactive hide details for "Grobauer, Bernd" ---09/21/2015 12:07:15 PM---Hi, stepping back from the choice of binding for a mome"Grobauer, Bernd" ---09/21/2015 12:07:15 PM---Hi, stepping back from the choice of binding for a moment, I would like to

From: "Grobauer, Bernd" <Bernd.Grobauer@siemens.com>
To: "cti@lists.oasis-open.org" <cti@lists.oasis-open.org>
Date: 09/21/2015 12:07 PM
Subject: [cti] Playing the "simpleton's advocate": how much complexity can we throw overboard?
Sent by: <cti@lists.oasis-open.org>





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







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