GPG 13 stands for the Good Practice Guide 13. It is a set of guidelines that were produced by the Communications-Electronics Security Group (CESG), which is a division of the UK’s Government Communications Headquarters (GCHQ). The CESG is the UK’s national technical authority for data assurance. The standards aim to produce a set of working practices that ensure data activities are properly enforced. The main avenue for data assurance oversight is the collection and collation of log messages that are generated by file systems, access rights management tools, and data management services.