This week, Christa and Si talk with Cyacomb's Graham Little and Mike Burridge about the technology it takes to identify child sexual abuse and terrorist imagery, on both devices and the online world. The balance between public safety and privacy is discussed, along with challenges faced by both social media providers preventing imagery from being shared, and law enforcement investigating the perpetrators. Also described: technological challenges and what they mean for investigations and prosecutions, including the need for training and education of users; and new developments coming from Cyacomb.