Community-building among groups of child abusers on the ‘dark web’ facilitates the large-scale distribution of indecent imagery and supports individuals in becoming more skilled, more dangerous offenders. Undercover police are tasked with posing as offenders to gather intelligence; however, we know little about the nature of these groups, and especially how one might approach them linguistically as an ‘authentically’ interested outsider. This study analyses rhetorical moves (Swales, 1990) in forum posts from child abuse-related dark web fora by self-identifying ‘newbies’ hoping to join established abuse communities. It identifies 12 distinct moves used in the pursuit to join online abuse communities and finds that expressions of competence and expertise are central to newbies’ attempts to gain community membership. ‘De-lurking’ is identified as a useful strategy in the performance of competence in online forums. These findings can support online undercover policing tasks as well as offender prioritisation.