# A Taxonomy for Security Flaws in Event-Based Systems
## 3 Taxonomy
### Literature Review Methodology
\begin{table}
\begin{tabular}{c c c} \hline \hline
**No.** & **Attack Type** & **Definition** \\ \hline A1 & Spoofing & For \(V_{1},V_{2},M_{1}\in C\) where \(V_{1}\
eq V_{2}\
eq M_{1}\) and \(\exists V_{1}\xrightarrow{e}V_{2}\) and (\(V_{2}\) contains \(f\)) and (\(M_{1}\xleftarrow{}V_{2}\))\(M_{1}\) sent a spoofed \(e\) to \(V_{2}\) to exploit \(f\) in \(V_{2}\) \\ \hline A2 & Interception & For \(V_{1},V_{2},M_{1}\in C\) where \(V_{1}\
eq V_{2}\
eq M_{1}\) and \(\exists V_{1}\xrightarrow{e}V_{2}\) and (\(e\) contains \(s\)) and (\(V_{1}\xleftarrow{}M_{1}\xleftarrow{}V_{1}\xleftarrow{}V_{2}\)): \\  & \(M_{1}\) intercepted \(e\), which was supposed to be sent to \(V_{2}\), to obtain \(s\) \\ \hline A3 & Eavesdropping & For \(V_{1},V_{2},M_{1}\in C\) where \(V_{1}\
eq V_{2}\
eq M_{1}\) and \(\exists V_{1}\xrightarrow{e}V_{2}\) and (\(e\) contains \(s\)) and (\(V_{1}\xleftarrow{}M_{1}\xleftarrow{}V_{2}\))\(M_{1}\) eavesdroped on \(e\), which was supposed to be open only to \(V_{2}\) to obtain \(s\) \\ \hline A4 & Confused & For \(V_{1},V_{2},M_{1}\in C\) where \(V_{1}\
eq V_{2}\
eq M_{1}\) and \(\exists(M_{1}\xleftarrow{}V_{1})\) and (\(V_{1}\) contains \(f\)) and (\(M_{1}\xleftarrow{}V_{2}\))\(\wedge(V_{2}\xleftarrow{}V_{1}\)): \\  & deputy & \(M_{1}\) accessed \(V_{1}\) by accessing \(V_{2}\), which can access \(V_{1}\), to exploit \(f\) in \(V_{1}\) \\ \hline A5 & Collusion & For \(V_{1},M_{1},M_{2}\in C\) where \(V_{1}\
eq M_{1}\
eq M_{2}\) and \(\exists(M_{1}\xleftarrow{}V_{1})\) and (\(V_{1}\) contains \(f\)) and (\(M_{1}\xleftarrow{}M_{2}\xleftarrow{}M_{2}\xleftarrow{}V_{1}\)): \\  & \(M_{1}\) colluded with \(M_{2}\), which can access \(V_{1}\), to exploit \(f\) in \(V_{1}\) \\ \hline A6 & Flooding & For \(V_{1},V_{2},M_{1}\in C\) where \(V_{1}\
eq V_{2}\
eq M_{1}\) and \(\exists V_{1}\xleftarrow{}V_{2})\) and (\(M_{1}\xleftarrow{}V_{2}\xleftarrow{}V_{1}\xleftarrow{}V_{2}\))\(\wedge\) \\  & (the number of \(e\)’s is overwhelmingly greater than the average number of \(e\)): \\  & \(M_{1}\) sent an overwhelming number of \(e\)’s to find \(V_{1}\) from accessing \(V_{2}\) \\ \hline A7 & Delaying & For \(V_{1},V_{2},V_{3},M_{1}\in C\) where \(V_{1}\
eq V_{2}\
eq V_{3}\
eq M_{1}\) and \(\exists(V_{1}\xleftarrow{}M_{1}\xleftarrow{}V_{2}\xleftarrow{}V_{3})\) and (\(V_{1}\xleftarrow{}M_{1}\xleftarrow{}V_{2}\xleftarrow{}V_{3}\))\(\wedge\) \\  & (the time interval between \(e\) and \(e_{1}\) is overwhelmingly larger than the time interval between \(e_{1}\) and \(e_{2}\)): \\  & \(M_{1}\) delayed the publication of \(e_{1}\) to make \(V_{2}\) and \(V_{3}\) malfunction \\ \hline \multicolumn{2}{c}{\(C\): a set of components, \(V\): a victim component, \(M\): a malicious component, \(f\): sensitive functionality, \(s\): sensitive information, \(e\): an event, \(x\xleftarrow{}^{\alpha}y\): an event communication channel for sending an event \(\alpha\) from \(x\) to \(y\), \(x\xleftarrow{}^{\alpha}y\): an event \(\alpha\) sent from \(x\) to \(y\).} \\ \end{tabular}
\end{table} 
Table 1: Types of Event Attacks. set of attribute keywords as specified in Table 2. Note that, to cover a larger number of literatures, synonyms were considered for the attribute keywords during the search process. For example, regarding \"vulnerability\", we also considered similar keywords such as \"flaw\" and \"error\". Because the scope of search for Android keywords is too large, in order to effectively collect the Android literature dealing with the characteristics of EBSs, we used \"android event\" and \"android intent\" as domain keywords. The selected keywords were applied to the search for the literatures' titles, abstracts, and tags. To exclude outdated literatures, we limited the scope of the search to literatures published from 2000 to 2020. Although the majority of the literatures regarding EBSs were almost a decade old, we decided to keep them if they had appeared in top-tier conferences or journals with significant contributions (H5-index \(\geq\) 20 or citation counts \(\geq\) 50).