Input Module plc's shortcomings

input module plc Disadvantages: module mechanism to bring safety hazard
1, the intercept system calls.
2, modify the output symbol table.
3, by modifying the system calls the plc temperature module themselves hidden.
4, redirect file operations.
5, modify the file owner.
6, plc controller suppliers processes.
7, the executable file redirection.
8, calling sys_socketcall by modifying the system, making the system after receiving the specified data packet open the back door
9, TTY hijacking.
10 virus.