Does Flashing Stock ROM in Odin Clear out the System Partition First? Does Flashing Stock Samsung ROM in Odin Clear out the System Partition First?

Options Used:
No repartition,
ROM put inside PDA slot

I'm wondering because I suspect there may have been some malware in the previous ROM that was flashed.  So I want to be sure all the Files that were in the System Partition Previously are deleted.
If you use Odin then I am asuming you have a samsung device. Depending on what Stock rom you use, I mean if you will flash using 1 file or 3 file rom, if you have a 3 file rom then you have to put in the pit file to, and then you can enable the re-partition.

If you use 1 file rom in odin, i think it will re-partition by default so you do not have to check the repartition check box in odin.