In this contemporary era, where a large part of the world population is deluged by extensive use of the internet and social media, terrorists have found it a potential opportunity to execute their vicious plans. They have got a befitting medium to reach out to their targets to spread propaganda, disseminate training content, operate virtually, and further their goals. To restrain such activities, information over the internet in context of terrorism needs to be analyzed to channel it to appropriate measures in combating terrorism. Open Source Intelligence (OSINT) accounts for a felicitous solution to this problem, which is an emerging discipline of leveraging publicly accessible sources of information over the internet by effectively utilizing it to extract intelligence. The process of OSINT extraction is broadly observed to be in three phases (i) Data Acquisition, (ii) Data Enrichment, and (iii) Knowledge Inference. In the context of terrorism, researchers have given noticeable contributions in compliance with these three phases. However, a comprehensive review that delineates these research contributions into an integrated workflow of intelligence extraction has not been found. The paper presents the most current review in OSINT, reflecting how the various state-of-the-art tools and techniques can be applied in extracting terrorism-related textual information from publicly accessible sources. Various data mining and text analysis-based techniques, that is, natural language processing, machine learning, and deep learning have been reviewed to extract and evaluate textual data. Additionally, towards the end of the paper, we discuss challenges and gaps observed in different phases of OSINT extraction.

中文翻译：

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恐怖主义相关信息的开源情报提取：综述

在当今时代，世界上很大一部分人口被互联网和社交媒体的广泛使用所淹没，恐怖分子发现这是执行其邪恶计划的潜在机会。他们有一个合适的媒介来接触他们的目标，以传播宣传、传播培训内容、虚拟操作并进一步实现他们的目标。为限制此类活动，需要对互联网上的恐怖主义信息进行分析，以将其引导至打击恐怖主义的适当措施。开源情报 (OSINT) 为这个问题提供了一个很好的解决方案，这是一门新兴学科，通过有效利用互联网来提取情报，利用互联网上可公开访问的信息源。广泛观察到 OSINT 提取的过程分为三个阶段（i）数据采集，（ii）数据丰富和（iii）知识推理。在恐怖主义的背景下，研究人员根据这三个阶段做出了显着的贡献。但是，尚未找到将这些研究贡献描述为情报提取集成工作流程的全面审查。该论文介绍了 OSINT 的最新评论，反映了如何应用各种最先进的工具和技术从可公开访问的资源中提取与恐怖主义相关的文本信息。已经回顾了各种基于数据挖掘和文本分析的技术，即自然语言处理、机器学习和深度学习，以提取和评估文本数据。此外，