Method and system for detecting fraudulent data update

A method and system for detecting fraudulent data update of databases (21, 31, 41) connected to a plurality of distributed computers (2, 3, 4) in which a monitor computer (1) connected via a network (5) to the distributed computers detects fraudulent data update. The monitor computer (1) collects initial data of the databases (21, 31, 41) of the distributed computers via the network (5) to generate parities for data at same storage fields and store them in a monitor database (11). Each time the databases (21, 31, 41) connected to the distributed computers are updated, a parity update unit (103) of the monitor computer generates new parities from data before and after the update and old parities and replace the old parities stored in the monitor database (11) by the new parities. At an auditing time, the monitor computer (1) collects latest data of the distributed databases (21, 31, 41), and generates parities which are compared with the corresponding parities already stored in the monitor database (11) to detect an inconsistency of both the parities.