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| import sys, os | |
| import argparse | |
| import math | |
| import pefile | |
| ''' | |
| Shannon-Entropy.py | |
| Determine Shannon Entropy of any file - value output between 0 (ordered) and 8 (fully random) | |
| Optinally add `-pe` argument to parse file headers of PE file and determine entropy for each header | |
| ''' | |
| def main(args=sys.argv[1:]): | |
| parser = argparse.ArgumentParser(description="Calculate Shannon entropy of input file") | |
| parser.add_argument('-file', '-f', help="Input file") | |
| parser.add_argument('-pe', help="BOOL: Specify if input file is PE for additional analysis", action="store_true") | |
| args = parser.parse_args(args) | |
| inFile = args.file | |
| pe = args.pe | |
| if not inFile: | |
| print("[-] ERROR! Missing input file parameter '-f'") | |
| sys.exit() | |
| file_path = inFile | |
| if not os.path.exists(file_path): | |
| print('File not found:', file_path) | |
| sys.exit() | |
| # Calculate entropy of input file | |
| entropy = calc_entropy_of_file(file_path) | |
| print("File Shannon Entropy:", entropy) | |
| # Do further analysis on headers if input file is PE | |
| if pe: | |
| peFile = pefile.PE(file_path, fast_load=True) | |
| # Enumerate each section to determine entropy | |
| for section in peFile.sections: | |
| print(section.Name.decode("utf-8")) | |
| print("Section entropy:", str(shannon_entropy(section.get_data()))) | |
| def shannon_entropy(data): | |
| # Determine the frequency of each byte value | |
| byte_counts = [0] * 256 | |
| for byte in data: | |
| byte_counts[byte] += 1 | |
| # Determine the probability of each byte value | |
| total_bytes = len(data) | |
| probabilities = [count / total_bytes for count in byte_counts if count > 0] | |
| # Determine Shannon entropy | |
| entropy = -sum(p * math.log2(p) for p in probabilities) | |
| return entropy | |
| def calc_entropy_of_file(file_path): | |
| with open(file_path, 'rb') as file: | |
| data = file.read() | |
| entropy = shannon_entropy(data) | |
| return entropy | |
| if __name__ == '__main__': | |
| main() |
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