This publication is a revision of IAEA Nuclear Security Series No. 8, Preventive and Protective Measures against Insider Threats, published in 2008. The new publication provides updated guidance to States, their competent authorities and operators, shippers and carriers on selecting, implementing, and evaluating measures for addressing insider threats. It applies to any type of nuclear facility, notably nuclear power plants, research reactors, and other nuclear fuel-cycle facilities (e.g. enrichment plants, reprocessing plants, fuel fabrication plants and storage facilities), whether in design, redesign, construction, commissioning, operation, shutdown or decommissioning.