A data processing apparatus has a plurality of storage elements residing at different physical locations within the apparatus, and fault history circuitry for detecting local transient faults occurring in each storage element, and for maintaining global transient fault history data based on the detected local transient faults. Analysis circuitry monitors the global transient fault history data to determine, based on predetermined criteria, whether the global transient fault history data is indicative of random transient faults occurring within the data processing apparatus, or is indicative of a coordinated transient fault attack. The analysis circuitry is then configured to initiate a countermeasure action on determination of a coordinated transient fault attack. This provides a simple and effective mechanism for distinguishing between random transient faults that may naturally occur, and a coordinated transient fault attack that may be initiated in an attempt to circumvent the security of the data processing apparatus.