Malicious codes may cause virus infections or threats of ransomware through symmetric encryption. Moreover, various bypassing techniques such as steganography, which refers to the hiding of malicious code in image files, have been devised. Unknown or new malware hidden in an image file in the form of malicious code is difficult to detect using most representative reputation- or signature-based antivirus methods. In this paper, we propose the use of ImageDetox method to neutralize malicious code hidden in an image file even in the absence of any prior information regarding the signatures or characteristics of the code. This method is composed of four modules: image file extraction, image file format analysis, image file conversion, and the convergence of image file management modules. To demonstrate the effectiveness of the proposed method, 30 image files with hidden malicious codes were used in an experiment. The malicious codes were selected from 48,220 recent malicious codes purchased from VirusTotal (a commercial application programming interface (API)). The experimental results showed that the detection rate of viruses was remarkably reduced. In addition, image files from which the hidden malicious code had previously been removed using a nonlinear transfer function maintained nearly the same quality as that of the original image; in particular, the difference could not be distinguished by the naked eye. The proposed method can also be utilized to prevent security threats resulting from the concealment of confidential information in image files with the aim of leaking such threats.

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