Abstract: A detection method of an illegal access to a computer system includes a step a) of collating user identification information inputted from an input unit in one or more log-in operations with user authentication information registered in the computer system, a step b) of detecting the number of times that the identification information is not coincident with the authentication information in a series of log-in operations within a predetermined term, a step c) of obtaining final log-in information indicating whether the identification information is coincident with the authentication information or not in a final log-in operation, and a step d) of comparing the number of times in respect to the incoincidence and the final log-in information with a predetermined judgment standard to thereby detect the presence of the illegal access.

Abstract: A computer for gathering log data includes a device for normalizing the log data by cutting out values corresponding to pre-defined data items from log data in log files of respective computers on the alert and re-arranging the values of data items defined, and storing the normalized log data therein and a device for gathering the stored normalized log data into a computer having a manager function. Further, when the normalized log data have log data output times corrected on the basis of a time of the computer having the manager function, the normalized log data are stored in order of the corrected log data output times.