Question: I'm studying algorithms to find connected components of graph., but I still don't know why is important to find connected components. In which applications do we use connected components of a graph?

Edit:
I want to know which graph analysis is dependent to the connected components of a graph? means that if i find the connected components of a graph, i can do that graph analysis easier. For example if i find the connected components, Can i cluster the graph easier? if yes, which graph analysis i can do better?

Thanks.

Answer: 
As you've already found out, any user can write to the event log with existing event sources.

You have to treat the event log as unsafe input, that could potentially have been manipulated and that you need to handle carefully.

Without more details on what you are trying to accomplish it's hard to give any more specific advice.
I may also add on to Anders Abel. Not only can it be written to, it can also be cleared without notice. This may have serious adverse affects to your program if not handled correctly.

There are ways to "secure" the event log using user permissions etc, however this doesn't stop applications or the system from changing the EventLog.