• Convergence Security Journal
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• v.18 no.3
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• pp.27-35
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• 2018

The certificate is electronic information issued by an accredited certification body to certify an individual or to prevent forgery and alteration between communications. Certified certificates are stored in PCs and smart phones in the form of encrypted files and are used to prove individuals when using Internet banking and smart banking services. Among the rapidly growing Android-based malicious applications are malicious apps that leak personal information, especially certificates that exist in the form of files. This paper proposes a method for judging whether malicious codes leak certificates by using DroidBox, an Android-based dynamic analysis tool.

• Proceedings of the KAIS Fall Conference
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• 2012.05b
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• pp.835-838
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• 2012

최근 스마트폰의 폭팔적인 증가와 함께 사용 환경개선도 이루어 지고 있다. 또한 Wi-Fi 존의 증가와 LTE같은 빠른 네트워크 환경은 사용자 중심의 수 많은 앱을 탄생시키고 있다. 안드로이드는 애플의 iOS와는 다른 오픈소스 정책으로 플랫폼 소스가 공개되어 있어 많은 개발자가 쉽게 접근이 가능하다. 그러나 안드로이드는 앱(App) 검증 체계가 미흡하기 때문에 악성코드 등으로 인한 위협요소가 존재하고 있다. 또한 파일 시스템은 임의적 접근제어방식으로 공격자가 취약점을 통해 관리자 권한을 얻어 시스템 자원을 제어할 수 있기 때문에 위협요소가 다분하다. 본 논문에서는 스마트폰 앱이 호출하는 시스템 API 및 네트워크 자원사용 패턴을 분석하여 부정 앱을 차단하는 방법을 제안하였다. 제안 방법으로 실험한 결과 API호출 빈도 및 자원 사용률이 최소 기준치 이하로 검출된 경우를 제외한 평가대상은 모두 검출하여 보안성 강화에 효과적인 것으로 실험을 통하여 검증하였다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.4
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• pp.921-928
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• 2016

Over the past few years, Smishing attacks such as malicious url and malicious application have been emerged as a major problem in South Korea since it caused big problems such as leakage of personal information and financial loss. Users are susceptible to Smishing attacks due to the fact that text message may contain curios content. Because of that reason, user could follow the url, download and install malicious APK file without any doubt or verification process. However currently Anti-Smishing App that adopted post-processing method is difficult to respond quickly. Users need a system that can determine whether the modification of the APK file and malicious url in real time because the Smishing can cause financial damage. This paper present the cloud-based system for verifying malicious url and malicious APK file in user device to prevent secondary damage such as smishing attacks and privacy information leakage.

• Journal of KIISE
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• v.44 no.4
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• pp.352-362
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• 2017

This paper analyzes security threats in Security Enhanced (SE) Android and proposes a new technique to efficiently protect application data including private information on rooted Android phones. On an unrooted device, application data can be accessed by the application itself according to the access control models. However, on a rooted device, a root-privileged shell can disable part or all of the access control model enforcement procedures. Therefore, a root-privileged shell can directly access sensitive data of other applications, and a malicious application can leak the data of other applications outside the device. To address this problem, the proposed technique allows only some specific processes to access to the data of other applications including private information by modifying the existing SEAndroid Linux Security Module (LSM) Hook function. Also, a new domain type of process is added to the target system to enforce stronger security rules. In addition, the proposed technique separates the directory type of a newly installed application and the directory type of previously installed applications. Experimental results show that the proposed technique can effectively protect the data of each application and incur performance overhead up to or less than 2 seconds.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.04a
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• pp.415-417
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• 2015

스마트폰이 출시된 이후 지금까지 개발된 안드로이드 앱은 초기 앱 자체의 문제가 있었으나 스마트폰 시장이 점차 확대 되면서 개발된 안드로이드 앱의 보안 취약점과 악성코드가 삽입된 어플리케이션의 .apk 파일 배포로 인해 무결성이 지켜지지 못하고 보안 문제가 끊임없이 발생하며 안드로이드폰에 설치된 앱의 위 변조로 악성코드가 삽입된 APK 파일을 이용해 설치하였을 경우 소스코드의 부정 사용과 개인정보유출 등 2 차로 금융사기 유도, 소액결재 등 사회적인 문제가 되고 있다. 본 논문은 위 변조된 안드로이드 어플리케이션의 진본 여부를 확인하 위해 방안을 제안하며 악의적인 목적으로 만들어진 위 변조된 안드로이드 어플리케이션 apk 파일을 이용한 설치로 부정 사용되는 안드로이드 어플리케이션의 진본 설치 여부를 진단할 수 있는 방안을 제안하고자 한다.

• Proceedings of the Korean Society of Computer Information Conference
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• 2022.07a
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• pp.321-322
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• 2022

스마트폰 사용자가 늘어남에 따라 갖춰줘야 할 보안성이 취약하여, 다양한 바이러스 및 악성코드 위험에 노출되어 있다. 안드로이드는 운영체제 중 가장 많이 사용되는 운영체제로, 개방성이 높으며 수많은 악성 앱 및 바이러스가 마켓에 존재하여 위험에 쉽게 노출된다. 2년 넘게 이어진 코로나 바이러스(Covid-19)으로 인해 꾸준히 위험도가 높아진 피싱공격(Phshing attack)은 현재 최고의 스마트폰 보안 위협 Top10에 위치한다. 본 논문에서는 딥러닝 기반 자연어처리 기술을 통해 피싱 공격 대응 방법 제안 및 실험 결과를 도출하고, 또한 향후 제안 방법을 보완하여 피싱 공격 및 다양한 모바일 보안 위협에 대응할 수 있는 앱을 설계할 것이다.

• KIPS Transactions on Software and Data Engineering
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• v.8 no.11
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• pp.427-432
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• 2019

In this paper, we propose three approaches to modeling Android malware. The first method involves human security experts for meticulously selecting feature sets. With the second approach, we choose 300 features with the highest importance among the top 99% features in terms of occurrence rate. The third approach is to combine multiple models and identify malware through weighted voting. In addition, we applied a novel method of eliminating permission information which used to be regarded as a critical factor for distinguishing malware. With our carefully generated feature sets and the weighted voting by the ensemble algorithm, we were able to reach the highest malware detection accuracy of 97.8%. We also verified that discarding the permission information lead to the improvement in terms of false positive and false negative rates.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.5
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• pp.309-316
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• 2014

It is easy to reverse engineer an Android app package file(APK) and get its decompiled source code. Therefore, attackers obtains economic benefits by illegally using the decompiled source code, or modifies an app by inserting malware. To address these problems in Android, we propose an APK overwrite scheme that protects apps against illegal modification of themselves by using a new anti-reverse engineering technique. In this paper, the targets are the apps which have been written by any programmer. For a target app (original app), server system (1) makes a copy of a target app, (2) encrypts the target app, (3) creates a stub app by replacing the DEX (Dalvik Executable) of the copied version with our stub DEX, and then (4) distributes the stub app as well as the encrypted target app to users of smartphones. The users downloads both the encrypted target app and the corresponding stub app. Whenever the stub app is executed on smartphones, the stub app and our launcher app decrypt the encrypted target app, overwrite the stub app with the decrypted target one, and executes the decrypted one. Every time the target app ends its execution, the decrypted app is deleted. To verify the feasibility of the proposed scheme, experimentation with several popular apps are carried out. The results of the experiment demonstrate that our scheme is effective for preventing reverse engineering and tampering of Android apps.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.3
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• pp.643-653
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• 2018

Xamarin is a representative cross-platform development framework that allows developers to write mobile apps in C# for multiple mobile platforms, such as Android, iOS, or Windows Phone. Using Xamarin, mobile app developers can reuse existing C# code and share significant code across multiple platforms, reducing development time and maintenance costs. Meanwhile, malware authors can also use Xamarin to spread malicious apps on more platforms, minimizing the time and cost of malicious app creation. In order to cope with this problem, it is necessary to analyze and detect malware written with Xamarin. However, little studies have been conducted on static analysis methods of the apps written in Xamarin. In this paper, we examine the structure of Android apps written with Xamarin and propose a static analysis technique for the apps. We also demonstrate how to statically reverse-engineer apps that have been transformed using code obfuscation. Because the Android apps written with Xamarin consists of Java bytecode, C# based DLL libraries, and C/C++ based native libraries, we have studied static reverse engineering techniques for these different types of code.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.3
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• pp.679-691
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• 2016

As vehicle started to contain many different communication devices, collecting external information became possible in IoT environment. In such environment, remotely controling vehicle is possible when vehicle information is obtained by looking in to vehicle network through smart device. However, android based smart device applications are vulnerable to malicious modulation and redistribution. Modulated android application can lead to vehicle information disclosure that could bring about vehicle control accident which becomes threat to drivers. furthermore, since vehicles today does not contain security methods to protect it, they are very vulnerable to security threats which can cause serious damage to users and properties. In this paper, many different vehicle management android applications that are sold in Google Play has been analyzed. With this information, possible threats that could happen in vehicle management applications are being analysed to prove the risks. the experiment is done on actual vehicle to prove the risks. Also, access control method to protect the vehicle against malicious actions that could happen through external network in IoT environment is suggested in the paper.