## 2 Research Selection Method

Table 3: Conferences, journals and books coding. 3 mitigation strategies used by the authors have been identified, these are specified in Table 6, including the \"others\" category, in order to assign a category to those proposals that do not adapt to the 3 identified strategies. Table 7 summarizes relevant data from 53 papers selected for this SLR according to Tables 3-6. The first column gives the author name and year of publications of the proposal. Column 2 refers to the number of citations the proposal has at the time of submission of this review. Column 3 shows type code according to Table 4. Column 4 refers to the journal or conference code, according to Table 3. Columns 5-10 specifies the theme code according to Table 5. Columns 11-14 detail the approach code according to the table. Finally, the last column shows the proposal's reference. \begin{table}
\begin{tabular}{c c} \hline \hline
**Type of Approach** & **Code** \\ \hline Based on authentication or cryptography & AC \\ Based on network monitoring & NM \\ Based on secure parent node selection & SP \\ Other & OT \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Approach coding: presents the mechanisms or strategies used by the authors to mitigate the attacks. \begin{table}
\begin{tabular}{c c} \hline \hline
**Theme** & **Code** \\ \hline Rank attack/Sinkhole attack & RSA \\ Selective forwarding/Blackhole attack & SBA \\ Wormhole attack & WA \\ DOGAG number version attack & DNA \\ DAO/DIS message inconsistency attack & D2A \\ Sybil attack & SA \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Theme coding. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Authors**} & \multirow{2}{*}{**Clinical**} & \multirow{2}{*}{**Type Code**} & \multirow{2}{*}{**JFCode**} & \multicolumn{6}{c}{**Time Code**} & \multicolumn{6}{c}{**Approation-Calling**} & \multicolumn{1}{c}{**Reference**} \\ \cline{6-13} \cline{5-13}  & & & & **  
Annual scientific productions are shown in Figure 2(a). Publications correspond to the years between 2011 and 2020. From this figure, it is concluded that the number of papers has increased over the years. However, throughout this period of time, the trend did not always increase, and there are some years in which production in the area decreased. Between the years 2011-2012, 2013-2014, and 2017-2019 there was a decrease of two, two, and six proposals, respectively. The most relevant decrease occurs between the years 2017 and 2018. Details of the subjects studied in this period are shown in Figure 2(b), it is observed that this decrease is mainly associated with the line of research associated with the subject RSA (Rank attack/Sinkhole attack) but there was an increase in research related to the D2A (DAO/DIS message inconsistency attack) issue. D2A is a group of two attacks that arise from the nature of RPL, affecting the DIO and DAO control messages. Therefore it can be concluded that, in 2018, researchers worked more to strengthen the security of the nature of the protocol compared to the previous year. For the rest of the subjects, the study remains almost constant. Figure 3: (**a**) Annual scientific production. (**b**) Themes by year. The most productive authors are shown in Figure 4. There are two authors with two papers, four authors with three papers, and four authors with four papers. The above shows that these authors show continuity in the research topic. Table 10 lists the contributions of the authors mentioned in Figure 4. From this table, we can obtain information that Figure 4 by itself does not provide. The authors [PERSON] and [PERSON] are listed in Figure 4 with three contributions each, although these contributions are the same for both authors. The same happens with the authors [PERSON], [PERSON], and [PERSON], for whom Figure 4 shows four contributions.