Nowadays, Android applications declare as many permissions as possible to provide more function for the users, which also poses severe security threat to them. Although many Android malware detection methods based on permissions have been developed, they are ineffective when malicious applications declare few dangerous permissions or when the dangerous permissions declared by malicious applications are similar with those declared by benign applications. This limitation is attributed to the use of too few information for classification. We propose a new method named fine-grained dangerous permission (FDP) method for detecting Android malicious applications, which gathers features that better represent the difference between malicious applications and benign applications. Among these features, the fine-grained feature of dangerous permissions applied in components is proposed for the first time. We evaluate 1700 benign applications and 1600 malicious applications and demonstrate that FDP achieves a TP rate of 94.5%. Furthermore, compared with other related detection approaches, FDP can detect more malware families and only requires 15.205 s to analyze one application on average, which demonstrates its applicability for practical implementation.

Aiming at the problem that the permission-based detection is too coarse-grained, a malware detection method based on sensitive application program interface(API) pairing is proposed. The method decompiles the application to extract the sensitive APIs corresponding to the dangerous permissions, and uses the pairing of the sensitive APIs to construct the undirected graph of malicious applications and undirected graph of benign applications. According to the importance of sensitive APIs in malware and benign applications, different weights on the same edge in the different graphs are assigned to detect Android malicious applications. Experimental results show that the proposed method can effectively detect Android malicious applications and has practical significance. 针对基于Android应用程序申请权限的检测过于粗粒度的问题，提出了基于敏感应用程序编程接口（application program interface，API）配对的恶意应用检测方法。通过反编译应用程序提取危险权限对应的敏感API，将敏感API两两配对分别构建恶意应用无向图与良性应用无向图，再根据恶意应用和良性应用在敏感API调用上的差异分配相同边不同的权重，以此检测Android恶意应用。实验结果表明，提出的方法可以有效地检测出Android恶意应用程序，具有现实意义。

Increasingly, malicious Android apps use various methods to steal private user data without their knowledge. Detecting the leakage of private data is the focus of mobile information security. An initial investigation found that none of the existing security analysis systems can track the flow of information through Unix domain sockets to detect the leakage of private data through such sockets, which can result in zero-day exploits in the information security field. In this paper, we conduct the first systematic study on Unix domain sockets as applied in Android apps. Then, we identify scenarios in which such apps can leak private data through Unix domain sockets, which the existing dynamic taint analysis systems do not catch. Based on these insights, we propose and implement JDroid, a taint analysis system that can track information flows through Unix domain sockets effectively to detect such privacy leaks.