A data processing method, apparatus, and computer program product for performing a similarity comparison between software programs are provided. An aspect of the invention provides a data processing method for performing a similarity comparison between two programs, where the data processing method includes: (a) extracting API names from each program and converting the API names to unique text sequences of a particular byte; (b) establishing a frequency table by counting a frequency of the extracted API names; (c) recording the API names converted into the unique text sequences in a log file in the order of extraction; and (d) saving the frequency table as a file and compressing the log file.