Structured Threat Information eXpression (STIX) is a standardized Extensible Markup Language (XML) programming language that is used to convey data about cybersecurity threats in a way that is easily understood by both humans and security technologies. The purpose of STIX is to provide a structured, open source, and free language for sharing cyberthreat intelligence (CTI) in a way that is both human- and machine-readable.
CTI is essential for organizations to understand the threats posed by cyber adversaries and to take appropriate action to minimize the negative impact of these threats. However, many organizations do not have access to adequate or relevant information, which hinders their ability to build accurate situational awareness of their threat landscape. STIX was developed to address this challenge by enabling security professionals and communities to capture and share CTI in a standardized and understandable way.
STIX has several core use cases in cybersecurity. It is used by threat analysts to review cyberthreats and identify patterns that could indicate cyberattacks. It is also used by cybersecurity decision-makers and operations personnel to facilitate and manage cyberthreat activities, including prevention, detection, and response. In addition, STIX enables the sharing of CTI within an organization and with outside partners or communities, which allows security teams to collaborate and improve their situational awareness of the threat landscape.
The architecture of STIX is based on eight core constructs that are independent, reusable, and interrelated. These constructs include observables, indicators, incidents, adversary tactics, techniques, and procedures (TTPs), exploit targets, courses of action, campaigns, and threat actors. These constructs are represented in an XML schema that provides a structured form for representing CTI.
STIX has evolved over time through community-driven efforts. It was first defined in 2012 with Version 0.3 and has since been refined and updated. The language is sponsored by the Office of Cybersecurity and Communications within the United States Department of Homeland Security (DHS) and is copyrighted by Mitre Corp. to ensure that it remains an open source, free, and extensible standard.
STIX is often used in conjunction with Trusted Automated eXchange of Indicator Information (TAXII), which is a method for exchanging CTI that is represented in STIX. TAXII serves as the transport mechanism for STIX, enabling organizations to share structured CTI in an open, standardized, secure, and automated manner.
Many organizations, both in the public and private sectors, use STIX and TAXII to share threat information with others. Examples include Microsoft, Hewlett Packard Enterprise, and numerous cybersecurity vendors.
In conclusion, STIX is a standardized XML programming language that enables the sharing of CTI in a structured and understandable way. It has been widely adopted in the cybersecurity community and is used to improve situational awareness, facilitate collaboration, and enhance cybersecurity-related capabilities. With its community-driven development and open nature, STIX continues to evolve and adapt to the changing cybersecurity landscape.