Rich Piazza
103 lines
7.0 KiB
Markdown
103 lines
7.0 KiB
Markdown
# Introduction
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This document describes how to query and manipulate CAPEC data in this repository. Machine-readable CAPEC data is available in
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a JSON-based [STIX 2.0](https://oasis-open.github.io/cti-documentation/stix/intro) and STIX 2.1 formats.
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STIX 2.x is just JSON and so should be very accessible from Python and other programming languages. If you are using Python, the [python-stix2](https://github.com/oasis-open/cti-python-stix2) library can help you work with the content as shown in the examples below.
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# Mapping Concepts
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First, we must describe how CAPEC objects and properties map to STIX 2.x objects and properties.
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## Objects
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In CAPEC, the main object is the Attack Pattern. Most Attack Pattern also have Mitigations. There are other types of objects in CAPEC (e.g, Category, View, etc.), but these are not (currently) part of the repository.
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The STIX types are found as literal strings assigned to the `type` property of the STIX JSON object. The STIX 2.x object called "Attack Pattern" corresponds to a CAPEC attack pattern. In STIX 2.x, there are objects called "Course(s) of Action" which can be used to describe CAPEC Mitigations.
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## Properties
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The following is a table mapping of CAPEC properties to STIX properties. Some of these properties are standard STIX properties, while others were custom-created for compatibility with CAPEC. These properties are accessed from STIX objects as JSON properties.
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### Attack Pattern
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| CAPEC 3.0 Property | CAPEC 2.7.1 Property | STIX Properties | STIX type |
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| --------------- | --------------- | --------------- | --------------- |
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**Name** | **Name** | `name` | string |
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**Description** | **Description/Summary** | `description` | string
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**Abstraction** | **Pattern\_Abstraction** |`x_capec_abstraction` | enumeration(`Meta, Standard, Detailed`)
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**Alternate\_Terms** | **Alternate\_Terms** | `x_capec_alternate_terms` | list(string)
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**Consequences** | **Attack\_Motivation-Consequences** | `x_capec_consequences` | dictionary(enumeration(`High, Medium, Low`), string)
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**Example\_Instances** | **Examples-Instances** | `x_capec_example_instances` | list(string)
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**Likelihood\_Of\_Attack** | **Typical\_Likelihood\_of\_Exploit/Likelihood** | `x_capec_likelihood_of_attack` | enumeration(`High, Medium, Low`)
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**Notes** | **Other\_Notes** | `x_capec_notes` | list(string)
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**Prerequisites** | **Attack\_Prerequisites** | `x_capec_prerequisites` | list(string)
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**Skills\_Required** | **Attacker\_Skills\_or\_Knowledge\_Required** | `x_capec_skills_required` | dictionary(string, enumeration(`High, Medium, Low`))
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**Typical\_Severity** | **Typical\_Severity** | `x_capec_typical_severity` | enumeration(`High, Medium, Low`)
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**ID** | **ID** | `external_references[i].external_id where external_references[i].source_name == "capec"` | integer
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**Related\_Weaknesses** | **Related\_Weaknesses** | `external_references[i].external_id where external_references[i].source_name == "cwe"` | integer
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**References** | **References** | `external_references[i].external_id where external_references[i].source_name == "reference_from_CAPEC"` | `external-reference`
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**Mitigation** | **Solutions\_and\_Mitigations** | `relationship_type == "mitigates"` | `relationship`
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CAPEC 3.0 properties not mapped (at this time): **Execution\_Flow**, **Indicators**, **Taxonomy\_Mappings**, **Content\_History**
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CAPEC 3.0 properties not appropriate to map: **Status**
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# Using Python and STIX 2.x
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In this section, we will describe how to query and manipulate CAPEC data that has been stored in a STIX 2.x repository. A Python library has been created for using and creating STIX 2.x data by the OASIS Technical Committee for Cyber Threat Intelligence, which develops the STIX standard. This library abstracts storage and transport details so that the same code can be used to interact with data locally on the filesystem or in memory, or remotely via [TAXII](https://oasis-open.github.io/cti-documentation/taxii/intro). The source code, installation instructions, and basic documentation for the library can be found [here](https://github.com/oasis-open/cti-python-stix2). There is a more thorough [API documentation](http://stix2.readthedocs.io/en/latest/overview.html) as well.
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## Python Library
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To begin querying STIX 2.x data, you must first have a [DataSource](http://stix2.readthedocs.io/en/latest/guide/datastore.html). For these examples, we will simply use a [FileSystemSource](http://stix2.readthedocs.io/en/latest/guide/filesystem.html). The CAPEC corpus must first be cloned or downloaded from [GitHub](https://github.com/mitre/cti).
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### Get all Attack Patterns
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Once the stix2 Python library is installed and the corpus is acquired, we need to open the DataStore for querying:
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```python
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from stix2 import FileSystemSource
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fs = FileSystemSource('./cti/capec')
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```
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When creating the DataSource, the keyword agrument `allow_custom` must be set to `True`. This is because the CAPEC data uses several custom properties which are not part of the STIX 2.x specification (`x_capec_prerequisites`, `x_capec_example_instances`, etc).
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To perform a query, we must define a [Filter](http://stix2.readthedocs.io/en/latest/guide/datastore.html#Filters). As of this writing, a filter must, at a minimum, specify object `id`'s or an object `type`. The following filter can be used to retrieve all CAPEC attack patterns:
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```python
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from stix2 import Filter
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filt = Filter('type', '=', 'attack-pattern')
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```
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Once this filter is defined, you can pass it to the DataSource `query` function in order to actually query the data:
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```python
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attack_patterns = fs.query([filt])
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```
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Notice that the `query` function takes a **list** of filters. These filters are logically AND'd together during the query. As of this writing, `allow_custom` must be set to `True` in order to query CAPEC data. This is because the CAPEC data uses several custom properties which are not part of the STIX 2.0 specification (`x_capec_prerequisites`, `x_capec_example_instances`, etc).
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**For the remaining examples, these imports and the FileSystemStore initialization will be omitted.**
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### Get any object by CAPEC ID
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In this example, the STIX 2.x type must be passed into the function. Here we query for the attack pattern with ID `66` (*SQL Injection*).
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```python
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def get_attack_pattern_by_capec_id(src, capec_id):
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filt = [
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Filter('type', '=', 'attack-pattern'),
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Filter('external_references.external_id', '=', 'CAPEC-' + capec_id),
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Filter('external_references.source_name', '=', 'capec'),
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]
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return src.query(filt)
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get_attack_pattern_by_capec_id(fs, '66')
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```
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### Get all Mitigations for specific Attack Pattern
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The mitigations for a technique are stored in objects separate from the technique. These objects are found through a `mitigates` relationship.
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```python
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def get_mitigations_by_attack_pattern(src, ap_stix_id):
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relations = src.relationships(ap_stix_id, 'mitigates', target_only=True)
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return src.query([
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Filter('type', '=', 'course-of-action'),
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Filter('id', 'in', [r.source_ref for r in relations])])
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ap = get_attack_pattern_by_capec_id(fs, '66')[0]
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get_mitigations_by_attack_pattern(fs, ap.id)
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```
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