Which statement about precursors and indicators is most correct? Indicators are the observable signals from an event, which may suggest that an information systems security event may happen later. Indicators are events that are part of an information security incident kill chain; warnings are the observable effects that we can detect, that tell us of the occurrence of the indicator. Precursors are events that prepare the way an attack, such as an intrusion, to take place. Precursors are the observable signals from an event, which may suggest that an information systems security event may happen later.