Self-service terminal

A self-service terminal ( 10 ) comprising a plurality of components associated with a valuable media, such as a card reader ( 28 ) or cash dispenser ( 30 ). Each component includes or is associated with one or more sensors for detecting potentially fraudulent activity and a component agent ( 34 ) for generating a warning signal in the event that such activity is detected. Also provided is a higher level agent ( 38 ) that is operable to receive warning signals from the component agents ( 34 ), and use the received signals to identify potentially fraudulent activity. By providing a hierarchy of fraud detection agents ( 34,38 ), the likelihood of a fraud being successfully detected is improved.