• Journal of Information Processing Systems
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• v.18 no.5
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• pp.650-664
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• 2022

Mobile applications can be easily downloaded and installed via markets. However, malware and malicious applications containing unwanted advertisements exist in these application markets. Therefore, smartphone users install applications with reference to the application review to avoid such malicious applications. An application review typically comprises contents for evaluation; however, a false review with a specific purpose can be included. Such false reviews are known as fake reviews, and they can be generated using artificial intelligence (AI)-based text-generating models. Recently, AI-based text-generating models have been developed rapidly and demonstrate high-quality generated texts. Herein, we analyze the features of fake reviews generated from Generative Pre-Training-2 (GPT-2), an AI-based text-generating model and create a model to detect those fake reviews. First, we collect a real human-written application review from Kaggle. Subsequently, we identify features of the fake review using natural language processing and statistical analysis. Next, we generate fake review detection models using five types of machine-learning models trained using identified features. In terms of the performances of the fake review detection models, we achieved average F1-scores of 0.738, 0.723, and 0.730 for the fake review, real review, and overall classifications, respectively.

• Journal of IKEEE
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• v.27 no.1
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• pp.93-102
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• 2023

As one of the techniques for analyzing malicious code, techniques creating a sequence or a graph of function call relationships in an executable program and then analyzing the result are proposed. Such methods generally study function calling in the executable program code through static analysis and organize function call relationships into a sequence or a graph. However, in the case of an obfuscated executable program, it is difficult to analyze the function call relationship only with static analysis because the structure/content of the executable program file is different from the standard structure/content. In this paper, we propose a dynamic analysis method to analyze the function call relationship of an obfuscated execution program. We suggest constructing a function call relationship as a graph using the proposed technique.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.5 no.2
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• pp.289-296
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• 2015

Java is an interpreted language that can run on a variety of platforms, also Java has a number of useful features for network. Due to theses features of Java language, Java is used in various fields. In this paper, we will talk about how the malware that threaten the Java Security Manager of the Java Virtual Machine is using the vulnerability of the Java Virtual Machine. And for corresponding measures, this paper suggest vulnerability analysis method of Java system class by using Java Call Graph and Java Access Permission Checking Tree. By suggesting that, we want to lay groundwork for preventing Java security threats in advance.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.5 no.2
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• pp.297-304
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• 2015

Zeus is one of the will-published malwares. Generally, it infects PC by executing a specific binary file downloaded on the internet. When infected, try to hook a particular Windows API of the currently running processes. If process runs hooked API, this API executes a particular code of Zeus and your private information is leaked. This paper describes techniques to detect and hook Windows API. We believe the technique should be able to detect modern P2P Zeus.

• Proceedings of the Korea Information Processing Society Conference
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• 2020.05a
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• pp.222-223
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• 2020

최근 악성코드로 인한 피해가 증가하고 있다. 악성코드는 악성코드가 속한 종류에 따라서 대응하는 방법도 다르기 때문에 악성코드를 종류별로 분류하는 연구도 중요하다. 기존에는 악성코드 시각화 과정을 통해서 생성된 악성코드의 글로벌 이미지를 사용해 악성코드를 각 종류별로 분류한다. 글로벌 이미지를 악성코드로부터 추출한 바이너리 정보를 사용해서 생성한다. 하지만, 글로벌 이미지만을 사용해서 악성코드를 각 종류별로 분류하는 경우 악성코드의 종류별로 중요한 특징을 고려하기 않기 때문에 분류 정확도가 떨어진다. 본 논문에서는 악성코드의 글로벌 이미지에 악성코드의 종류별 특징을 나타내기 위한 로컬 특징 기반 글로벌 이미지를 사용한 악성코드 분류 방법을 제안한다. 첫 번째, 악성 코드로부터 바이너리를 추출하고 추출된 바이너리를 사용해서 글로벌 이미지를 생성한다. 두 번째, 악성 코드로부터 로컬 특징을 추출하고 악성코드의 종류별 핵심 로컬 특징을 단어-역문서 빈도(Term Frequency Inverse Document Frequency, TFIDF) 알고리즘을 사용해 선택한다. 세 번째, 생성된 글로벌 이미지에 악성코드의 패밀리별 핵심 특징을 픽셀화해서 적용한다. 네 번째, 생성된 로컬 특징 기반 글로벌 이미지를 사용해서 컨볼루션 모델을 학습하고, 학습된 컨볼루션 모델을 사용해서 악성코드를 각 종류별로 분류한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2022.11a
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• pp.905-907
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• 2022

악성코드를 분석하는 기존 기법인 정적분석은 빠르고 효율적으로 악성코드를 탐지할 수 있지만 난독화된 파일에 취약한 반면,, 동적분석은 난독화된 파일에 적합하지만 느리고 비용이 많이 든다는 단점을 가진다. 본 연구에서는 두 분석 기법의 단점을 해결하기 위해 딥러닝 모델을 활용한 난독화에 강한 정적분석 모델을 제안하였다. 본 연구에서 제안한 방법은 원본 코드 및 난독화된 파일을 grayscale 이미지로 변환하여 데이터셋을 구축하고 AutoEncoder 를 사전학습시켜 encoder 가 원본 파일과 난독화된 파일로부터 원본 파일의 특징을 추출할 수 있도록 한 이후, encoder 의 output 을 fully connected layer 의 입력으로 넣고 전이학습시켜 악성코드를 탐지하도록 하였다. 본 연구에서는 제안한 방법론은 난독화된 파일에서 악성코드를 탐지하는 성능을 F1 score 기준 14.17% 포인트 향상시켰고, 난독화된 파일과 원본 파일을 전체를 합친 데이터셋에서도 악성코드 탐지 성능을 F1 score 기준 7.22% 포인트 향상시켰다.

• Proceedings of the Korean Society of Computer Information Conference
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• 2023.01a
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• pp.103-106
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• 2023

코로나 팬데믹 사태로 인해 업무환경이 재택근무를 하는 환경으로 바뀌고 악성코드의 변종 또한 빠르게 발전하고 있다. 악성코드를 분석하고 백신 프로그램을 만들면 새로운 변종 악성코드가 생기고 변종에 대한 백신프로그램이 만들어 질 때까지 변종된 악성코드는 사용자에게 위협이 된다. 본 연구에서는 머신러닝 알고리즘을 사용하여 악성파일 여부를 예측하는 방법을 제시하였다. 일반적인 악성코드의 구조를 갖는 Portable Executable 구조 파일을 파이썬의 LIEF 라이브러리를 사용하여 Certificate, Imports, Opcode 등 3가지 feature에 대해 정적분석을 하였다. 학습 데이터로는 정상파일 320개와 악성파일 530개를 사용하였다. Certificate는 hasSignature(디지털 서명정보), isValidcertificate(디지털 서명의 유효성), isNotExpired(인증서의 유효성)의 feature set을 사용하고, Imports는 Import Address Table의 function 빈도수를 비교하여 feature set을 구축하였다. Opcode는 tri-gram으로 추출하여 빈도수를 비교하여 feature set을 구축하였다. 테스트 데이터로는 정상파일 360개 악성파일 610개를 사용하였으며 Feature set을 사용하여 random forest, decision tree, bagging, adaboost 등 4가지 머신러닝 알고리즘을 대상으로 성능을 비교하였고, bagging 알고리즘에서 약 0.98의 정확도를 보였다.

• Journal of applied mathematics & informatics
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• v.41 no.6
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• pp.1257-1274
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• 2023

Rotating machines heavily rely on an intricate network of interconnected sub-components, with bearing failures accounting for a substantial proportion (40% to 90%) of all such failures. To address this issue, intelligent algorithms have been developed to evaluate vibrational signals and accurately detect faults, thereby reducing the reliance on expert knowledge and lowering maintenance costs. Within the field of machine learning, Artificial Immune Systems (AIS) have exhibited notable potential, with applications ranging from malware detection in computer systems to fault detection in bearings, which is the primary focus of this study. In pursuit of this objective, we propose a novel procedure for detecting novel instances of anomalies in varying operating conditions, utilizing only the signals derived from the healthy state of the analyzed machine. Our approach incorporates AIS augmented by Dynamic Time Warping (DTW). The experimental outcomes demonstrate that the AIS-DTW method yields a considerable improvement in anomaly detection rates (up to 53.83%) compared to the conventional AIS. In summary, our findings indicate that our method represents a significant advancement in enhancing the resilience of AIS-based novelty detection, thereby bolstering the reliability of rotating machines and reducing the need for expertise in bearing fault detection.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.24 no.1
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• pp.31-40
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• 2014

In Korea, the Public Key Infrastructure (PKI) has been introduced. For secure information transmission and identification, the electronic signature authorization system of a certificate-based is built, and then the service provide.The certificate is stored in location what users can easily access and copy. Thus, there is a risk that can be stolen by malware or web account hacking. In addition, private key passwords can be exposed by the logging tool, after keyboard security features are disabled. Each of these security weaknesses is a potential conduit for identity theft, property/asset theft, and theft of the actual certificates. The present study proposes a method to prevent the private key file access illegally. When a certificate is stored, the private key is encrypted by the dependent element of the device, and it is stored securely. If private key leakage occurs, the retrieved key could not be used on other devices.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.4
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• pp.895-902
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• 2016

Smart phone distribution rate has been rising and it's security threat also has been rising. Especially Android smart phone reaches nearly 85% of domestic share. Since repackaging on android smart phone is relatively easy, the number of re-packaged malwares has shown steady increase. While many detection techniques have been proposed in order to prevent malwares, it is not easy to detect re-packaged malwares by static analysis and it is also difficult to operate dynamic analysis in android smart phone. Static analysis proposed in this paper features code reuse of repackaged malwares. We extracted DEX files from android applications and performed static analysis using class names and method names. This process doesn't not include reverse engineering, so it is possible to detect malwares efficiently.