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The Package construct serves as a container for grouping sets of related content. That content might be related because it’s part of the same report or it might be as simple as it’s being published at the same time. The package gives that context a wrapper and allows for metadata to be described about the content as a group.
A STIX Campaign represents a set of TTPs, incidents, or threat actors that together express a common intent or desired effect. For example, an adversary using a particular set of TTPs (malware and tools) to target an industry sector with a specific intent may constitute a campaign. In the STIX data model, campaigns represent both that intent itself and, perhaps more importantly, act as a meta-construct to relate the associated TTPs, incidents, and threat actors that are part of that campaign together.
A STIX Course of Action component is used to convey information about courses of action that may be taken either in response to an attack or as a preventative measure prior to an attack. They are used to express both courses of action that might be taken (are possible options are are suggested) in the course of an incident to respond to something that has occurred or to mitigate the effect of an exploit target (vulnerability or misconfiguration) apriori.
The course of action component itself contains information about the objective of the action, its efficacy, its likely impact, cost, structured parameter observables, and even a structured course of action meant to be implemented automatically in a tool.
A STIX Exploit Target conveys information about a technical vulnerability, weakness, or misconfiguration in software, systems, or networks that may be targeted for exploitation by an adversary. The exploit target component leverages current standard approaches in identifying and describing vulnerabilities through the suggested option of using CVE and/or OSVDB IDs to identify named vulnerabilities, CVRF to describe 0-day or other unnamed vulnerabilities, and CVSS to score vulnerabilities. Additionally, CCE is used as the suggested method to identify configuration items and CWE as a mechanism for representing software weaknesses.
A STIX Incident conveys information about a cyber security incident. This may be the most familiar STIX construct to those with a background in computer security and incident response. As you’d expect, it contains a good deal of information about what occurred, the impact of the incident on systems and information, the incident timeline, points of contact, and other descriptive information.
In the STIX relationship model, incidents can be related to the threat actors involved, the campaigns that they’re a part of, courses of action that were taken or were suggested, indicators that were used to detect the incident or were discovered as part of the investigation, TTPs that were used to carry out the incident, and observables that were detected during the incident.
A STIX Indicator conveys specific Observable patterns combined with contextual information intended to represent artifacts and/or behaviors of interest within a cyber security context. They consist of one or more Observable patterns potentially mapped to a related TTP context and adorned with other relevant metadata on things like confidence in the indicator’s assertion, handling restrictions, valid time windows, likely impact, sightings of the indicator, structured test mechanisms for detection, related campaigns, suggested courses of action, related indicators, the source of the Indicator, etc. Recognizing limitations in current standardized approaches of representation, STIX leverages community knowledge and best practices to define a new Indicator structure for representing Indicator information.
A STIX Threat Actor conveys information that characterizes or identifies (or both) an adversary. The characterization consists of information like the sophistication of the threat actor, its motivations and desired effects, and historically observed behavior. In the STIX relationship model, threat actors also include information such as observed TTPs, historic (or current) campaigns, and other threat actors that appear associated with this actor.
TTP is a military term that means “tactics, techniques, and procedures”. In STIX it is used to represent adversarial behavior, such as what victims they target, what attack patterns and malware they use, and what resources (infrastructure, tools, personas) they leverage. Because it describes adversary behavior, which is a big part of STIX, the TTP construct is one of the most commonly used and expressive constructs. In the STIX relationship structure, TTPs are referenced from indicators to describe which TTPs an indicator indicates, from campaigns and threat actors to describe the TTPs that are leveraged in a campaign or by a threat actor, in an incident to describe which TTPs were used in the execution of an attack, and to other TTPs to describe relationships of various sorts among TTPs. TTPs also use the exploit target construct to describe which exploit targets a TTP might exploit.