• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.6
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• pp.1431-1439
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• 2017

In the security field, log analysis is important to detect malware or abnormal behavior. Recently, image visualization techniques for malware dectection becomes to a major part of security. These techniques can also be used in online games. Users can leave a game when they felt bad experience from game bot, automatic hunting programs, malicious code, etc. This churning can damage online game's profit and longevity of service if game operators cannot detect this kind of events in time. In this paper, we propose a new technique of PNG image conversion based churn prediction to improve the efficiency of data analysis for the first. By using this log compression technique, we can reduce the size of log files by 52,849 times smaller and increase the analysis speed without features analysis. Second, we apply data mining technique to predict user's churn with a real dataset from Blade & Soul developed by NCSoft. As a result, we can identify potential churners with a high accuracy of 97%.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.34 no.1
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• pp.31-40
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• 2024

Recently, static analysis-based signature and pattern detection technologies have limitations due to the advanced IT technologies. Moreover, It is a compatibility problem of multiple architectures and an inherent problem of signature and pattern detection. Malicious codes use obfuscation and packing techniques to hide their identity, and they also avoid existing static analysis-based signature and pattern detection techniques such as code rearrangement, register modification, and branching statement addition. In this paper, We propose an LLVM IR image-based automated static analysis of malicious code technology using machine learning to solve the problems mentioned above. Whether binary is obfuscated or packed, it's decompiled into LLVM IR, which is an intermediate representation dedicated to static analysis and optimization. "Therefore, the LLVM IR code is converted into an image before being fed to the CNN-based transfer learning algorithm ResNet50v2 supported by Keras". As a result, we present a model for image-based detection of malicious code.

• Journal of KIISE
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• v.43 no.12
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• pp.1325-1333
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• 2016

Software classification has several applications such as copyright infringement detection, malware classification, and software automatic categorization in software repositories. It can be also employed by software filtering systems to prevent the transmission of illegal software. If illegal software is identified by measuring software similarity in software filtering systems, the average number of comparisons can be reduced by shrinking the search space. In this study, we focused on the classification of Windows executables using API call information and machine learning. We evaluated the classification performance of machine learning-based classifier according to the refinement method for API information and machine learning algorithm. The results showed that the classification success rate of SVM (Support Vector Machine) with PolyKernel was higher than other algorithms. Since the API call information can be extracted from binary executables and machine learning-based classifier can identify tampered executables, API call information and machine learning-based software classifiers are suitable for software filtering systems.

• Smart Media Journal
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• v.8 no.1
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• pp.27-34
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• 2019

Ransomware is a malicious program code evolved into various forms of attack. Unlike traditional Ransomware that is being spread out using email attachments or infected websites, a new type of Ransomware, such as WannaCryptor, may corrupt files just for being connected to the Internet. Due to global Ransomware damage, there are many studies conducted to detect and defense Ransomware. However, existing research on Ransomware detection only uses Ransomware signature database or monitors specific behavior of process. Additionally, existing Ransomware detection methods hardly detect and defense a new Ransomware that behaves differently from the traditional ones. In this paper, we propose a method to detect Ransomware by arranging decoy files and analyzing the method how Ransomware accesses and operates files in the file system. Also, we conduct experiments using proposed method and provide the results of detection and defense of Ransomware in this paper.

• The Journal of the Korea Contents Association
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• v.15 no.10
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• pp.607-615
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• 2015

Mosts user of internet and smart phone has certificate, and uses it when money transfer, stock trading, on-line shopping, etc. Mosts user stores certificate in a hard disk drive of PC, or the external storage medium. In particular, the certification agencies are encouraged for user to store certificate in external storage media such as USB memory rather than a hard disk drive. User think that the external storage medium is safe, but when it is connect to a PC, certificate may be copied easily, and can be exposed to hackers through malware or pharming site. Moreover, if a hacker knows the user's password, he can use user's certificate without restrictions. In this paper, we suggest secure management scheme of the private key file using a password of the encrypted private key file, and a USB Memory's hardware information. The private key file is protected safely even if the encrypted private key file is copied or exposed by a hacker. Also, if the password of the private key file is exposed, USB Memory's container ID, additional authentication factor keeps the private key file safe. Therefore, suggested scheme can improve the security of the external storage media for certificate.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.1
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• pp.67-77
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• 2017

A protector is a software for protecting core technologies by using compression and encryption. Nowadays malwares use the protector to conceal the malicious code from the analysis. For detailed analysis of packed program, unpacking the protector is a necessary procedure. Lately, most studies focused on finding OEP to unpack the program. However, in this case, it would be difficult to analyze the program because of the limits to remove protecting functions by finding OEP. In this paper, we studied about the protecting functions in the Themida and propose an unpacking technique for it.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.2
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• pp.251-258
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• 2017

Most malware, including Ransomware, is built for the Windows operating system. This is because it is more harmful to target an operating system with a high share. But in recent years, MacOS's operating system share has steadily increased. As people become more and more used, the number of malicious code running on the MacOS operating system is increasing. Ransomware has been known to Korea since 2015, and damage cases are gradually increasing. MacOS is no longer free from Ransomware, as Ransomware for MacOS was discovered in March 2016. In order to cope with future Ransomware, this paper used Ransomware's modified file extension to detect Ransomware. We have studied how to detect and block Ransomware processes by distinguishing between extensions changed by the user and extensions changed by the Ransomware process.

• The Journal of the Convergence on Culture Technology
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• v.2 no.1
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• pp.79-85
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• 2016

Ransomware was a malicious code that active around the US, but now it spreads rapidly all over the world and emerges in korea recently because of exponential computer supply and increase in users. Initially ransomware uses e-mail as an attack medium in such a way that induces to click a file through the spam mail Pam, but it is now circulated through the smart phone message. The current trend is an increase in the number of damage, including attacks such as the domestic large community site by ransomware hangul version. Ransomware outputs a warning message to the user to encrypt the file and leads to monetary damages and demands for payment via bitcoin as virtual currency is difficult to infer the tracking status. This paper presents an analysis and solutions to damage cases caused by ransomware.

• KIPS Transactions on Computer and Communication Systems
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• v.7 no.6
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• pp.155-164
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• 2018

Many malicious programs have been compressed or encrypted using various commercial packers to prevent reverse engineering, So malicious code analysts must decompress or decrypt them first. The OEP (Original Entry Point) is the address of the first instruction executed after returning the encrypted or compressed executable file back to the original binary state. Several unpackers, including PinDemonium, execute the packed file and keep tracks of the addresses until the OEP appears and find the OEP among the addresses. However, instead of finding exact one OEP, unpackers provide a relatively large set of OEP candidates and sometimes OEP is missing among candidates. In other words, existing unpackers have difficulty in finding the correct OEP. We have developed new tool which provides fewer OEP candidate sets by adding two methods based on the property of the OEP. In this paper, we propose two methods to provide fewer OEP candidate sets by using the property that the function call sequence and parameters are same between packed program and original program. First way is based on a function call. Programs written in the C/C++ language are compiled to translate languages into binary code. Compiler-specific system functions are added to the compiled program. After examining these functions, we have added a method that we suggest to PinDemonium to detect the unpacking work by matching the patterns of system functions that are called in packed programs and unpacked programs. Second way is based on parameters. The parameters include not only the user-entered inputs, but also the system inputs. We have added a method that we suggest to PinDemonium to find the OEP using the system parameters of a particular function in stack memory. OEP detection experiments were performed on sample programs packed by 16 commercial packers. We can reduce the OEP candidate by more than 40% on average compared to PinDemonium except 2 commercial packers which are can not be executed due to the anti-debugging technique.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.9
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• pp.2040-2048
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• 2010

In contemporary society, though convenience and efficiency of work using information system is growing high, adverse effect problems of malignant code, system hacking, information leak by insiders due to the development of the network are raising their head daily. Because of this, enormous work forces and expenses for the recovery and management of system is needed. The existing system can be divided into two aspects: security solution which surveils and treats virus and malignant codes, and network management solution which observes the system of computer, and practices maintenance and repair such as management, recovery, backup. This treatise applied Active Write Filter mechanism and the technology based on NFS and complemented the maintenance problems of user data of the existing system and designed the system which enables solving problems of intellectual property right such as information protection and illegal work.