Since emerging as a global extremist movement, the Islamic State has expanded its influence in Indonesia, where its supporters persist despite intensive counter-terrorism efforts. IS-related recruitment and attacks have been ongoing since 2014. Through in-depth interviews with 33 convicted or active IS supporters, as well as insights from Indonesian security personnel, including representatives from BIN, BNPT, Densus 88 AT and BAIS, the study has identified thirteen factors that enable these networks to endure. These factors fall into two main categories: nine dominant factors that directly underpin the organisational and ideological survival of the group, and four supporting factors that provide flexibility and localised adaptability. The findings emphasise the importance of shifting counterterrorism strategies from a reactive approach to proactively disrupting ideological, technological and community-based support systems. © UNISCI, 2025.