diff --git a/rfcs/text/0021-threat-enrichment.md b/rfcs/text/0021-threat-enrichment.md index 70f7b55ab3..9975402c4d 100644 --- a/rfcs/text/0021-threat-enrichment.md +++ b/rfcs/text/0021-threat-enrichment.md @@ -1,13 +1,7 @@ # 0021: Threat Enrichment - -- Stage: **0 (strawperson)** -- Date: **2021-05-03** - - +- Stage: **1 (draft)** +- Date: **2021-06-10** +As these fields represent the enrichment of an existing event with indicator information, they are comprised of three categories of data: + +1. The indicator's indicator fields, as defined in RFC 0018 +2. Other relevant ECS fields from the indicator (see below) +3. Fields representing the context of the enrichment itself + +### Proposed new fields + +Field | Type | Example | Description +--- | --- | --- | --- +threat.enrichments.matched.atomic | keyword | 2f5207f2add28b46267dc99bc5382480 | The value that matched between the event and the indicator +threat.enrichments.matched.id | keyword | db8fb691ffdb4432a09ef171659c8993e6ddea1ea9b21381b93269d1bf2d0bc2 | The _id of the indicator document that matched the event +threat.enrichments.matched.index | keyword | threat-index-000001 | The _index of the indicator document that matched the event +threat.enrichments.matched.field | keyword | host.name | Identifies the field on the enriched event that matched the indicator +threat.enrichments.matched.type | keyword | indicator_match_rule | Identifies the type of the atomic indicator that matched a local environment endpoint or network event. + @@ -39,12 +50,128 @@ Stage 2: Add or update all remaining field definitions. The list should now be e Stage 1: Describe at a high-level how these field changes will be used in practice. Real world examples are encouraged. The goal here is to understand how people would leverage these fields to gain insights or solve problems. ~1-3 paragraphs. --> +### Adding threat intelligence match/enrichment to another document + +If it is determined that an event matches a given indicator, that event can be enriched with said indicator. Presently, Indicator Match Detection rules will perform that enrichment automatically, but ad hoc/manual enrichment is an expected feature that analysts will leverage in the future. + +#### Example document + +```json5 +{ + "process": { + "name": "svchost.exe", + "pid": 1644, + "entity_id": "MDgyOWFiYTYtMzRkYi1kZTM2LTFkNDItMzBlYWM3NDVlOTgwLTE2NDQtMTMyNDk3MTA2OTcuNDc1OTExNTAw", + "executable": "C:\\Windows\\System32\\svchost.exe" + }, + "message": "Endpoint file event", + "@timestamp": "2020-11-17T19:07:46.0956672Z", + "file": { + "path": "C:\\Windows\\Prefetch\\SVCHOST.EXE-AE7DB802.pf", + "extension": "pf", + "name": "SVCHOST.EXE-AE7DB802.pf", + "hash": { + "sha256": "0c415dd718e3b3728707d579cf8214f54c2942e964975a5f925e0b82fea644b4" + } + }, + "threat": { + "enrichments": [ + { + // Each enrichment is added as a nested object under `threat.enrichments.*` + // Copy all the object indicators under `indicator.*`, providing full context + "indicator": { + "marking": { + "tlp": "WHITE" + }, + "first_seen": "2020-10-01", + "last_seen": "2020-11-01", + "sightings": 4, + "type": ["sha256", "md5", "file_name", "file_size"], + "description": "file last associated with delivering Angler EK" + }, + // event and file fields are copied from the indicator doc, if relevant + "event": { + "provider": "Abuse.ch", + "dataset": "threatintel.abusemalware", + "module": "threatintel", + "reference": "https://system.example.com/event/#0001234" + }, + "file": { + "hash": { + "sha256": "0c415dd718e3b3728707d579cf8214f54c2942e964975a5f925e0b82fea644b4", + "md5": "1eee2bf3f56d8abed72da2bc523e7431" + }, + "size": 656896, + "name": "invoice.doc" + }, + /* `matched` will provide context about which of the indicators above matched on this + particular enrichment. If multiple matches for this indicator object, this could + be a list */ + "matched": { + "atomic": "0c415dd718e3b3728707d579cf8214f54c2942e964975a5f925e0b82fea644b4", + "field": "file.hash.sha256", + "id": "abc123f03", + "index": "threat-indicators-index-000001", + "type": "indicator_match_rule" + } + } + ] + }, + // Tag the enriched document to indicate the threat enrichment matched + "tags": ["threat-match"], + // This should already exist from the original ingest pipeline of the document + "related": { + "hash": ["0c415dd718e3b3728707d579cf8214f54c2942e964975a5f925e0b82fea644b4"] + } +} +``` + +### Proposed enrichment pipeline mechanics pseudocode + +1. Original document completes its standard pipeline for the given source (i.e. filebeat module pipeline) +2. Original document is sent to "threat lookup" pipeline +3. For each indicator type, we perform the following (a file sha256 for example): + - if exists "file.hash.sha256": + - enrich processor: + "policy_name": "file-sha256-policy", + "field" : "file.hash.sha256", + "target_field": "threat_match", + "max_matches": "1" + - policy file-sha256-policy: + "match": { + "indices": "threat-\*", + "match_field": "file.hash.sha256", + "enrich_fields": ["event", "file", "indicator"] + } + - set: + field: "threat_match.matched.type" + value: "file-sha256-policy" + - set: + field: "threat_match.matched.field" + value: "file.hash.sha256" + - set: + field: "threat_match.matched.atomic" + value: "{{ file.hash.sha256 }}" + - set: + field: "threat.enrichments" + value: [] + override: false + - append: + field: "threat.enrichments" + value: "{{ threat_match }}" + - remove: + field: "threat_match" + +**NOTE**: There may be some optimization on which enrichments we attempt based upon the event categorization fields. For instance, we know that data that presents the netflow model or "interface" doesn't contain a sha256 hash. Since those categorization fields are lists, if data presented as both netflow and file (for whatever reason), then we'd check both network-related lookups and file-related lookups + ## Source data +Source data are ECS indicator documents as specified RFC 0008. At present, the best source of these documents is the [filebeat threatintel module](https://github.com/elastic/beats/tree/master/x-pack/filebeat/module/threatintel). + @@ -69,6 +196,10 @@ The goal here is to research and understand the impact of these changes on users Stage 1: Identify potential concerns, implementation challenges, or complexity. Spend some time on this. Play devil's advocate. Try to identify the sort of non-obvious challenges that tend to surface later. The goal here is to surface risks early, allow everyone the time to work through them, and ultimately document resolution for posterity's sake. --> +I believe this format should actually simplify much of the enrichment logic originally proposed in RFC 0008, since a naive implementation would simply copy the fields directly from each indicator document into `threat.enrichments`, and add the appropriate `matched` fields. + +While not a concern for ECS consumers at large, our existing experimental implementation within Kibana Security Solution will have to change significantly (for the better!), with accompanying data migration: https://github.com/elastic/kibana/issues/100510 + @@ -82,6 +213,7 @@ Stage 3: Document resolutions for all existing concerns. Any new concerns should The following are the people that consulted on the contents of this RFC. * @rylnd | author +* @devonakerr | sponsor - ## References @@ -108,6 +239,7 @@ e.g.: * Stage 0: https://github.com/elastic/ecs/pull/1386 +* Stage 1: https://github.com/elastic/ecs/pull/1400