Strange behavior after formatting a flash drive?

Question

Malware

I connected the USB flash drive to the infected computer, decided immediately after that to format it in fat32 in a clean system, and then a strange, previously unnoticed behavior occurs - at first the occupied space on the flash drive is 4096 or 8192, and after a few seconds it changes to 12kb or 24kb and so on, then there are triples depending on the selected cluster size. And with another same 8GB flash drive formatted in a different system, this does not happen, the size remains the same as the size of the cluster, that is, 4096. What is it, could a virus get into the system in the first case and so disguise itself on flash drive?
Literally the following is happening. If I format in ntfs: cluster size
increases by 1 cluster
size 4096 bytes: busy on flash drive 27992064 - in three seconds 27996160 = 4096
cluster size 8192 bytes: busy on the flash drive 27893760 - after three seconds 27901952 = 8192
If I format in fat32:
increases by 2 cluster sizes
2048: busy 2048 - after three seconds 6144
4096: 4096 - 12288
8192: 8192 - 24576
16384 - 16384: 4 and so on
For fun, I risked a clean flash drive, which I formatted on a clean system with a cluster size of 4096 - that's how much occupied space remains forever - inserted it into a system in which suspicious behavior is observed - and VZHUKH - 12288 bytes are occupied even without formatting, simply because inserted it. What's going on, I have no idea? Both windows 8.1 systems, clean system on ssd, strange on hdd

Answer 1

Perhaps the virus is registered in the boot sector (if any) or a hidden partition. Why bother at all? Format the flash drive completely and lie down the infected computer.