TIMFuser: A multi-granular fusion framework for cyber threat intelligence

Cyber attack campaigns with multiple technical variants are becoming increasingly sophisticated and diverse, posing great threats to institutions and every individual. Cyber Threat Intelligence (CTI) offers a novel technical solution to transition from passive to active defense against cyber attacks. To counter these attacks, security practitioners need to condense CTIs from extensive CTI sources, primarily in the form of unstructured CTI reports. Unstructured CTI reports provide detailed threat information and describe multi-step attack behaviors, which are essential for uncovering complete attack scenarios. Nevertheless, automatic analysis of unstructured CTI reports is challenging. Furthermore, manual analysis is often limited to a few CTI sources. In this paper, we propose a multi-granular fusion framework for CTIs from massive CTI sources, comprising a comprehensive pipeline with six subtasks. Many current CTI extraction systems are limited by mining intelligence from a single source, thereby leading to challenges such as producing a fragmented view of attack campaigns and lower value density. We fuse the attack behaviors and attack techniques of the attack campaigns using innovative and improved multi-granular fusion methods and offer a comprehensive view of the attack. TIMFuser fills a critical gap in the automated analysis and fusion of multi-source CTIs, especially in the multi-granularity aspect. In our evaluation of 739 real-world CTI reports from 542 sources, experimental results demonstrate that TIMFuser can enable security analysts to obtain a complete view of real-world attack campaigns, in terms of fused attack behaviors and attack techniques.