With the increasing popularity of social networks and chat rooms, new risks for children
and adolescents are emerging. In particular, they are exposed to the danger of sexual online
grooming. To address this problem, technical approaches have been developed to assist
law enforcement in investigating sexual online grooming and protect young people while
chatting. This chapter aims to approach the issue of sexual online grooming from a technical
point of view. Research in this area has focused on developing methods to detect sexual
online grooming in chats automatically. These methods already achieve a high level of
reliability. Thus, they provide essential support for law enforcement agencies in analysing
the often immense amount of chatlogs for evidence of sexual online grooming. In addition,
technical approaches can assist investigators in undercover work, sometimes required to
convict sexual offenders. This includes automatically generating a summary of the linguistic
habits of the person whose identity the police officer intends to assume. Moreover, chatbots
posing as adolescents to attract sexual offenders have been suggested. Furthermore, this
chapter describes how semi-automatic and automatic linguistic methods can be used to
analyse the phases of the sexual online grooming process and presents real-time protection
tools against sexual online grooming.