Good points John! So, since there appears to be robust library support for manipulating ISO8601-formatted date/time values and since it allows the representation of reduced-precision values (such as a date + hour or date + hour + minute), is there any reason why we can’t agree on this and move on? From: cti-stix@lists.oasis-open.org [mailto:cti-stix@lists.oasis-open.org] On Behalf Of Wunder, John A.
Sent: Tuesday, November 24, 2015 6:55 PM
To: cti-stix@lists.oasis-open.org
Subject: Re: [cti-stix] STIX timestamps and ISO 8601:2000 After thinking about this for a bit and seeing all of the back and forth (in particular Alex’s e-mail below), it occurs to me that maybe the right answer is just to use ISO8601 as-is. It’s a standard for a reason after all - ISO 8601 is an international standard. There are libraries in many languages that are able to parse it [1,2,3,4,5]. As Alex says, we’ll have better luck getting tools to adopt an RFC or ISO standard vs. getting them to use something we invent. - ISO 8601 supports arbitrary precision. Most libraries will zero-out the precision, which is perfect for simple consumers: that’s exactly what we’ve discussed. If on the other hand your application cares about precision you may be able to find a library to do it (the advantage of an international standard) or you may have to do it yourself. But this is fine: simple things are simple, complicated things are more complicated. - I tend to agree with Alex on timezones. As long as the timezone is specified it shouldn’t matter what we use. Let’s again just go with the existing standard and allow offsets or UTC (so long as some kind of timezone is specified). - ISO 8601 also supports things like duration…for our purposes, we would want to limit it to actual timestamps. To summarize: handling dates and times in programming is hard [6] and we could spend weeks trying to find the perfect solution. Let’s focus on cyber threat intelligence though and use the existing international standard for dates and times. Also, in all of my decisions I think: is there an XKCD comic about this? Yes, there is: https://xkcd.com/1179/ Please do not mandate that times in STIX / TAXII must be in UTC. It seems to me that one of the benefits of ISO 8601 / RFC 3339 timestamps is including the time zone offset from UTC. We have years of experience with this at $dayjob, where many logs that might eventually be parsed into STIX start from times represented in local time zones. In our experience, “defaulting” to UTC leads to all sorts of people / process / technology side effects, such as when a parser assumes UTC inputs and the person utilizing the parser does not know or realize to write the logic to convert local time into UTC. I think we will have better luck getting tools to adopt an RFC or ISO standard for how they put times into logs (versus Unix timestamps, etc.) than to convince them to always log in UTC or to always output a time in any given format and then indicate a time zone elsewhere. I think I could come on board with that... Bret Jordan CISSP Director of Security Architecture and Standards | Office of the CTO PGP Fingerprint: 63B4 FC53 680A 6B7D 1447 F2C0 74F8 ACAE 7415 0050 "Without cryptography vihv vivc ce xhrnrw, however, the only thing that can not be unscrambled is an egg." Yes please. A lot of languages will handle this automatically when parsing ISO 8601 timestamps so it probably isn’t a *huge* deal, but every step we take to make things more consistent is a positive in my book. John Regarding timezone, I’ve always thought that we should be mandating all times should be UTC at the STIX/CybOX level. It should be up to the UI tools to display that UTC time in whatever timezone the viewer is in. We always made our logging tools record in UTC timezone, as it meant that we could capture data from around the world and it would make sense. Always having UTC makes it trivial when pulling together dates from many and varied places across the world. Rather than forcing specification of timezone, I would just like to mandate that the timezone will always be UTC, and that the tools that use STIX will do the translation when they present it to the user. Senior STIX Subject Matter Expert SOLTRA | An FS-ISAC and DTCC Company One of the changes we made in STIX 1.1 was the addition of a “precision” attribute next to all timestamps (except for @timestamp, which was intended to always be precise to the second or millisecond). The intent was to allow producers to convey times that were precise to a millisecond/second (possible in ISO 8601), day, month, and year (not possible in ISO 8601). The use case was incident and report timestamps where implying millisecond or even second precision was not accurate…the incident was reported on a given day and so the full timestamp would need to fake the time portion of the day. To be honest I’m not sure that that use case is important enough to introduce the concept of precision, but we did explicitly add it in 1.1 so it’s something we should at least consider as an alternative to always requiring millisecond precision even in cases where’s it’s essentially faked. The other thing STIX added on top of that is that timezone is “strongly suggested” (it’s optional in 8601). I’d be in favor of making it required unless any implementors have objections. The problem is the "subset" potion. ISO 8601 actually does not specify how to represent milliseconds. So some people don't include it, some do, sometimes they also throw in nanoseconds...
I think we should extend ISO 8601 in the spec to include milliseconds and make it mandatory, so that it is well known exactly what the time format will be. Millisecond resolution will be required for many pieces of software operating with STIX.
-
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
<graycol.gif>Jerome Athias ---11/19/2015 11:48:25 PM---Back to the future ---------- Forwarded message ----------
From: Jerome Athias <athiasjerome@gmail.com>
To: cti-stix@lists.oasis-open.org
Date: 11/19/2015 11:48 PM
Subject: [cti-stix] Fwd: STIX timestamps and ISO 8601:2000
Sent by: <cti-stix@lists.oasis-open.org>
Back to the future
---------- Forwarded message ----------
From: Jerome Athias <athiasjerome@gmail.com>
Date: 2014-02-10 10:10 GMT+03:00
Subject: Re: STIX Content Revision and Revocation
To: "Wunder, John A." <jwunder@mitre.org>
Cc : Terry MacDonald <terry.macdonald@gmail.com>, Patrick Maroney
<Pmaroney@specere.org>, "Grobauer, Bernd"
<Bernd.Grobauer@siemens.com>, "Taylor, Marlon"
<Marlon.Taylor@hq.dhs.gov>, DisplayName <patrick.maroney@mac.com>,
"Barnum, Sean D." <sbarnum@mitre.org>, Kyle Maxwell
<krmaxwell@gmail.com>, Dave Dittrich <dittrich@u.washington.edu>,
stix-discussion-list Structured Threat Information _expression_/ST
<stix-discussion-list@lists.mitre.org>
I would see xs:datetime as "an implementation of strings formatted
according to a subset of ISO 8601:2000, documented in RFC 3339."
http://www.w3.org/TR/xmlschema-2/#isoformats
http://tools.ietf.org/html/rfc3339
so no "differences"
2014-02-10 Wunder, John A. <jwunder@mitre.org>:
> Hey guys,
>
>
>
> I have a quick question about RFC3339 vs. XML Schema's dateTime. I looked
> into them briefly and as far as I can tell they are very similar...some small
> differences in what each allows (capital T to denote time vs. either capital
> or lowercase, things like that). Are there important differences that make
> RFC3339 better than xs:dateTime that I'm missing? The nice thing about
> xs:dateTime is that, as long as STIX is in XML it natively validates, vs.
> RFC3339 which we would have to validate (and wouldn't work as well in
> programmatic bindings).
>
>
>
> Note: I'm basing this off of this mailing list post regarding Atom, so it's
> very possible I just don't understand the differences:
> http://www.imc.org/atom-syntax/mail-archive/msg13103.html.
>
>
>
> Thanks,
>
> John
>
>
>
> From: Terry MacDonald [mailto:terry.macdonald@gmail.com]
> Sent: Sunday, February 09, 2014 8:20 PM
> To: Patrick Maroney
> Cc: Grobauer, Bernd; Taylor, Marlon; DisplayName; Barnum, Sean D.; Wunder,
> John A.; Kyle Maxwell; Dave Dittrich; stix-discussion-list Structured Threat
> Information _expression_/ST
> Subject: Re: STIX Content Revision and Revocation
>
>
>
> [+1] again on the RFC3339 (In UTC with 6 digits of precision) for me too
> please.
>
>
>
> Cheers
>
>
>
> Terry MacDonald
>
>
> Terry MacDonald
>
>
>
> On 10 February 2014 14:02, Patrick Maroney <Pmaroney@specere.org> wrote:
>
> [+1] For a universal (optional) timestamp attribute( (RFC3339 in UTC with
> at last 6 digits of precision for 'time-secfrac'). Understand we will need
> to defer on other related attributes (like potential CRUD/change modality)
> to give it the attention this needs However, this change would help lay
> the foundations for a unified temporal reference (or at least the ability to
> assert same ;-).
>
>
>
> Patrick Maroney
> Executive Director
> Defense Security Information Exchange (DSIE)
> Office: (856)983-0001
> Cell: (609)841-5104
> pmaroney@specere.org
>
> ________________________________
>
> From: owner-stix-discussion-list@lists.mitre.org
> <owner-stix-discussion-list@lists.mitre.org> on behalf of Grobauer, Bernd
> <Bernd.Grobauer@siemens.com>
> Sent: Sunday, February 09, 2014 2:48:01 PM
> To: Taylor, Marlon; DisplayName; Barnum, Sean D.
>
>
> Cc: Wunder, John A.; Terry MacDonald; Kyle Maxwell; Dave Dittrich;
> stix-discussion-list Structured Threat Information _expression_/ST
>
> Subject: RE: STIX Content Revision and Revocation
>
>
>
> Hi,
>
>
>
> I pretty much agree with Marlon's answers to the open questions put by Sean.
> Looking at
>
> draft 2 of version 1.1 of Stix, I would like to add my vote to Marlon's
> answer to question
>
> 10 "Should an additional @timestamp attribute be added to each contstruct.".
> Marlon
>
> prefers the attribute, and so do I: timestamp information is such essential
> information,
>
> that it should be on top-level right next to the identifier rather than
> somewhere below
>
> in the (optional!!) "Information_Source/Time/Produced_Time" element.
>
>
>
> Also: I think on must be able to add timestamp information to really every
> object
>
> that has an identifier: I am not sure that every object I want to timestamp
> has the 'Information_Source'-substructure:
>
> making '@timestamp' an attribute next to any place where an '@id' attribute
> occurs makes sure
>
> that any object can be timestamped.
>
>
>
> So, in short: although this comes rather late in the timeline of STIX 1.1: I
> really think
>
> that draft 2 should be changed with regards to the location of where the
> timestamp information
>
> is kept: make '@timestamp' a sibling of '@id', '@id_ref' and
> '@timestamp_ref' rather
>
> than keeping the timestamp in "Information_Source/Time/Produced_Time".
>
>
>
> Kind regards,
>
>
>
> Bernd
>
>
>
>
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