# Malware Detection Issues, Challenges, and Future Directions: A Survey
## 5 The Taxonomy of Feature Extraction and Representation Methods
### Feature Extraction Methods
#### 5.1.1 N-Gram
\begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Reference**} & \multicolumn{3}{c}{**Feature Engineering**} & \multicolumn{3}{c}{**Model Type**} & \multicolumn{3}{c}{**Model Mode**} & \multicolumn{3}{c}{**Detection Approach**} \\ \cline{2-11}  & **Feature Extraction** & **Feature Representation** & **Binary- Class** & **Multi- Class** & **Fechnique** & **General** & **Specific** & **Signature-** & **Behavioral-** & **Heuristic-** \\ \hline
[43] & Text mining & Weight-based vector & ✓ & & ✓ & & ✓ & ✓ & ✓ & & \\
[72] & Frequency-based extractor, N-gram & Binary-based vector & ✓ & & SVM & ✓ & & ✓ & & ✓ & \\
[45] & Frequency-based extractor & Binary-based vector & ✓ & & SVM & ✓ & & & & ✓ \\
[46] & Frequency-based extractor & Weight-based vector & ✓ & & AMA & & ✓ & & & ✓ \\
[39] & Graph-based extractor & Weight-based vector & & K-NN, SVM & & & & ✓ & & \\
[35] & Frequency-based extractor & Frequency-based vector & ✓ & & RF & & ✓ & ✓ & & \\
[38] & N-gram & Binary-based vector & ✓ & & K-NN & ✓ & & ✓ & & \\
[39] & Graph-based extractor & Weighted dependency graph & ✓ & & ✓ & & ✓ & & ✓ & \\
[38] & Iterative-based extractor & Weight-based vector & & ✓ & J48, K-NN & & ✓ & & ✓ & \\
[40] & Text mining & Rule-based representation & ✓ & & ✓ & & ✓ & & & ✓ \\
[41] & Frequency-based extractor & Binary-based vector & ✓ & & SVM & ✓ & & ✓ & & \\
[42] & N-gram, Frequency-based extractor, & Image characterization-based vector & ✓ & ✓ & XGBost & ✓ & & & ✓ & \\ Gray-scale image-based extractor & & & Weight-based vector & ✓ & & RF & ✓ & & ✓ & \\
[43] & N-gram & Weight-based vector & ✓ & & MC & ✓ & & ✓ & \\
[44] & Word embedding & Weight-based vector & ✓ & & SVM & ✓ & & ✓ & \\
[45] & N-gram & Frequency-based vector & ✓ & & WIM & ✓ & & ✓ & \\
[46] & Graph-based extractor & Binary-based vector & & & HLES-MMI & ✓ & & ✓ & \\
[47] & N-gram & Weight-based vector & ✓ & & & ✓ & ✓ & ✓ & \\
[48] & N-gram & Image characterization-based vector & ✓ & & LR & ✓ & & & ✓ \\
[49] & Gray-scale image-based extractor & Image characterization-based vector & ✓ & SVM, CNN & ✓ & & ✓ & \\
[50] & N-gram, Frequency-based extractor & Frequency-based vector & ✓ & & XGBost & ✓ & & ✓ & \\
[51] & Word embedding & Weight-based vector & ✓ & & CNN & ✓ & & & ✓ \\
[52] & Frequency-based extractor & Weight-based vector & ✓ & & CS & ✓ & & & ✓ \\
[53] & Frequency-based extractor & Binary-based vector & ✓ & & SVM & ✓ & & ✓ & \\
[54] & Graph-based extractor & Weighted dependency graph & ✓ & ✓ & & ✓ & & ✓ & ✓ \\
[55] & Frequency-based extractor & Rule-based representation & ✓ & & ✓ & ✓ & & ✓ & ✓ \\
[56] & Frequency-based extractor & Weight-based vector & & JSD & ✓ & ✓ & & ✓ & \\
[57] & Gray-scale image-based extractor & Image characterization-based vector & & ✓ & CNN & ✓ & ✓ & & ✓ \\
[58] & Gray-scale image-based extractor & Image characterization-based vector & & ✓ & SVM & ✓ & ✓ & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Summary of detection approaches, extraction, and representation methods.