In this paper, we studied the performance of feature extraction methods according to the size of N-gram for malware detection. The feature is extracted by three methods, using Opcode Only, both Opcode and API and API Only from PE file. We measure the performance of them indirectly with measuring the AUC score and accuracy of classifier. We did experiments with the different N size by using several classifiers such as DT, SVM, KNN and BNB classifiers. As a result, we got the conclusion as followings. If we use N-gram technique, we recommend Opcode Only method through our experiments. Also, the instance-based classifier KNN and DT among the model based classifier have good performance than SVM and BNB.

In this paper, we propose a Difference Image Entropy based gaze direction recognition system. The Difference Image Entropy is computed by histogram levels using the acquired difference image of current image and reference images or average images that have peak positions from -255 ∼ +255 to prevent information omission. There are two methods about the Difference Image Entropy based gaze direction. 1) The first method is to compute the Difference Image Entropy between an input image and average images of 45 images in each location of gaze, and to recognize the directions of user's gaze. 2) The second method is to compute the Difference Image Entropy between an input image and each 45 reference images, and to recognize the directions of user's gaze. The reference image is created by average image of 45 images in each location of gaze after receiving images of 4 directions. In order to evaluate the performance of the proposed system, we conduct comparison experiment with PCA based gaze direction system. The directions of recognition left-top, right-top, left-bottom, right-bottom, and we make an experiment on that, as changing the part of recognition about 45 reference images or average image. The experimental result shows that the recognition rate of Difference Image Entropy is 97.00% and PCA is 95.50%, so the recognition rate of Difference Image Entropy based system is 1.50% higher than PCA based system.