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Malware is often hidden in illegitimately cloned software. Android, with over two billions active devices, is one of the most affected platforms because code cloning is quite simple and there are several not controlled markets. Obfuscation is both a cause and a solution to this scenario: a cause because obfuscated malware is harder to detect, a solution because obfuscation of legitimate applications makes code cloning more difficult. A deeper understanding of the obfuscation techniques would lead to more effective and aware use. In the literature, there are few methods of obfuscation detection with limited accuracy. Manual reverse engineering is too time-consuming to achieve this purpose, we need faster and automated techniques. In this work, we propose several deep learning models that can detect and classify the presence of obfuscation in Android applications. In addition to classical ML methods, we leverage natural language processing or image recognition approaches, then with a hybrid model, we exploit the best of each approach. Tests over a large dataset, made using different obfuscation tools, showed improvements compared to previous obfuscation detection methods. We target four obfuscation classes: identifier renaming, string encryption, reflection and class encryption, achieving an average F-measure of 0.985. [ABSTRACT FROM AUTHOR]

In this paper, we present a behavioral biometric-based smartphone user authentication mechanism, namely, AnswerAuth , which relies on the very common users' behavior. Behavior, here, refers to the way a user slides the lock button on the screen, to unlock the phone, and brings the phone towards her ear. The authentication mechanism works with the biometric behavior based on the extracted features from the data recorded using the built-in smartphone sensors, i.e., accelerometer, gyroscope, gravity, magnetometer and touchscreen, while the user performed sliding and phone-lifting actions. We tested AnswerAuth on a dataset of 10,200 behavioral patterns collected from 85 users while they performed the unlocking actions, in sitting, standing , and walking postures, using six state-of-the-art conceptually different machine learning classifiers in two settings, i.e., with and without simultaneous feature selection and classification. Among all the chosen classifiers, Random Forest (RF) classifier proved to be the most consistent and accurate classifier on both full and reduced features and provided a True Acceptance Rate (TAR) as high as 99.35%. We prototype proof-of-the-concept Android app, based on our findings, and evaluate it in terms of security and usability. Security analysis of AnswerAuth confirms its robustness against the possible mimicry attacks. Similarly, the usability study based on Software Usability Scale (SUS) 1 1 https://www.usability.gov/how-to-and-tools/methods/system-usability-scale.html. questionnaire verifies the user-friendliness of the proposed scheme (SUS Score of 75.11). Experimental results prove AnswerAuth as a secure and usable authentication mechanism. [ABSTRACT FROM AUTHOR]

While encryption can prevent unauthorized access to a secret message, it does not provide undetectability of covert communications over the public network. Implementing a highly latent data exchange, especially with low eavesdropping/discovery probability, is challenging for practical scenarios, such as social and political movements in authoritarian regimes, military operations, and privacy preservation. Moreover, the current literature suffers from a low embedding capacity and monolingual applicability, limiting the amount of hiding secret data within short text messages using state-of-the-art algorithms, e.g., linguistic-based, structural-based, or coverless-based solutions. In this paper, we present a systematic covert communication technique called CovertSYS that enables a multilingual secure end-to-end conversation via messaging or social network platforms. The CovertSYS functions by encrypting a confidential message using a multi-factor authentication scheme and converting the encoded binary data into hidden Unicode symbols to be transmitted under cover of short text messages. We then conduct extensive experiments to confirm the security and validity of the proposed technique against state-of-the-art approaches. Our experimental results show that the CovertSYS provides a superior mean performance of 91.53% by improving the criteria scores: embedding capacity rate of 100%, imperceptibility rate of 76.4%, and distortion robustness rate of 98.2%. Finally, we discuss the practical implications of the proposed technique compared to the existing text steganography methods. [Display omitted] • Various evaluation criteria based on literature and practical scenario have been discussed. • Possible cyberattacks on covert communication systems have been described. • The CovertSYS has been implemented in an Android prototype software. • Experimental results show superior performance compared to existing related works. [ABSTRACT FROM AUTHOR]