F9->Shift-F9 Exception passing in Olly

[D-Jester]

Programs often use this type of protection to make it difficult to trace the execution of the program

When an application runs into an exception while its debugged, the debugger will halt (pause).
EXE packers use this to see if the program handles the exception or (if its being debugged) not.
This is done by setting up what it called a Structured Exception Handler (SEH) it is usually set up right before an exception.
The program pushes the "handler" this is where execution will continue at if the program handles it own exceptions.
By pressing SHIFT + F9 you pass the exception to the application and allow it to continue as it normally would even if it weren't debugged.
These exception occur even if the program isn't being debugged, you just don't see them because they are automtically handled by the program.
If you just press F9, F7, F8...etc the program detects that execution did not continue as it should have and terminates itself, or windows terminates it because the exception was not handled.

Some Reading Material:
hxxp://msdn.microsoft.com/library/en-us/ debug/base/structured_exception_handling.asp

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