Incidents of child sexual abuse (CSA) are frequently documented and have recently attracted intense police, public scrutiny and efforts of social control across the Western world. This paper aims to explore the very concerning issue of online CSA and the way in which the police is responding to this growing problem. It will present some of the challenges the police in the United Kingdom face daily in dealing with the threats to children’s online safety. It argues that although proactive undercover policing has helped police forces to unmask sex offenders who predate innocent victims online, the advancement of technology is making the work of police officers more and more challenging. The findings presented have been collected over the last decade (2003-2013) during two exploratory, grounded theory studies, which involved the interviews with 21 police officers and forensic examiners and the observation and analysis of three police operations at the London Metropolitan Police Paedophile Unit in London.