A STIX file is an XML file saved in the Structured Threat Information eXpression (STIX) format. It is created by various computer security organizations so it can be shared for analysis and archived. STIX files contain information about security threats, which include any indicators of compromise such as IP addresses that are suspected to be malicious.

STIX is a language designed to describe cyber threat information for a network. It is intended for users responsible for defending systems such as malware analysts, security tool vendors, threat sharing communities, cyber threat analysts, and security researchers. It is saved in the XML format to allow its information to be shared, stored, and analyzed in a common language.