How to reinstall firmware to be sure there aren't malware?

[secon25]

I have a s3 with version 4.3, and i have read that malware may remain also after a hard reset, because malware can infect the firmware. So i would like to reinstall firmware (i don't want to change firmware, i only want reinstall 4.3), i see this guide https://forum.xda-developers.com/galaxy-s3/general/guide-how-to-reinstall-stock-firmware-t1978840 , what do you think about it? If i follow this guide,can i to be sure my S3 firmware is safe? P.S sorry for my bad English

 

[B. Diddy]

Try using Samsung Kies to reinstall the firmware. Otherwise, you could use Odin, getting the firmware from SamMobile (which is pretty well-regarded): http://forums.androidcentral.com/am...w-flash-stock-rom-via-odin-new-interface.html

 

[smvim]

Both sammobile and updato are reliable sources for stock Samsung ROMs. Both verify their downloads, just note that sammobile intentionally restricts the bandwidth on its download servers so even if you have a fast connection on your end don't be surprised at how long it takes to download a ROM from them.
https://www.sammobile.com/firmwares/
Download Firmware – Samsung Update
As for the link you provided also note that XDA Developers has a very good reputation and postings there are often a reference used by many.
Regarding Kies, that's the more or less official Samsung utility to manage updates/upgrades to your phone. Odin, on the other hand, is essentially the 'non-official' utility to manage a Samsung device (it's actually a Samsung-developed utility that was leaked out to the public a few years ago). So when Kies isn't working out for you, using Odin allows more flexibility as you're manually manipulating your device. Also, Odin being a Windows program if you don't have access to a Windows PC there's also an Open Source alternative utility, Heimdall.

 

[secon25]

Thanks for the answers, so first i'll try to follow the guide usingi Samsung Kies, if i get some problems, i'll try to use Odin

 

[B. Diddy]

Super response, @smvim!