After identifying the research questions, the next step is searching for relevant primary studies. To this end, search sources are identified and the searching string is proposed in this section. In order to find the data of relevant publications, we use the following five digital libraries:
- IEEE Xplore Digital Library: https://ieeexplore.ieee.org
- ACM Digital Library: https://dl.acm.org
- Springer Link: https://link.springer.com
- Science Direct: https://www.sciencedirect.com
- Wiley Online Library: https://onlinelibrary.wiley.com
To ensure that we did not overlook any significant relevant work, we conducted further searching processes on two of the most popular research citation engines:
- Google Scholoar: https://scholar.google.com/
- Web of Knowledge: https://webofknowledge.com/
Only those studies related to deep learning based Android malware analysis should be included to further review, so the publication that meets any of the following exclusion criteria would be viewed as an irrelevant paper and would be dismissed from the preliminary result set. The following exclusion criteria are considered for selecting primary studies:
- Non-English written literature.
- Duplicate papers or similar studies with different versions from the same authors.
- Studies of which their full texts are inaccessible.
- Studies belonging to books, thesis, monographs, keynotes, panels, or venues not executing the peer-review process.
- Studies presenting reviews or surveys.
- Studies presenting malware analysis in non-Android platforms (e.g., iOS, Windows, Linux).
- Papers presenting analyses of cyber attacks or Android Operating System (OS).
- Papers presenting analyses of Android applications but not focusing on malicious behaviors (e.g., Application categories in Android markets)
- Literature not using deep learning techniques
Obtaining all relevant studies doesn't mean that we are able to identify the final list of papers, since it is impossible that the quality of all selected studies is desirable. For this reason, we defined a quality appraisal criterion (QAC) shown in below:
- QAC1 Is the research published in high-level venues?
- QAC2 Are the motivations of the research clearly stated?
- QAC3 Dose the study clearly described proposed techniques
- QAC4 Are the experimental setups such as experimental environments and the information of datasets described in detail?
- QAC5 Dose the study clearly validate the experimental results?
- QAC6 Are the contributions and limitations of the study listed explicitly?
- QAC7 Dose the study contribute to the academic or industrial community?