I found a folder named: 89y5ron9.default, C:\Users\x\AppData\Local\Mozilla\Firefox\Profiles\89y5ron9.default , and its over 1.5 GB large, over 25000 files inside. On google this search didnt match to antything. what is it?

Question

after i delete it, it's few days without it and after that it shows again with lots of files and takes a lot of space. I tryed to search on google but without results. My scanning program spends 15 min to check this folder (longer tahn all other parts of HDD)
hope u will answer me
thanks.

Answer 1

That's your browser cache folder. The name is randomized so it's unlikely to come up in a search. If you want to manage the size of the cache folder rather than letting Firefox use the amount of space it likes, you can do that here:
orange Firefox button ''or'' Tools menu > Options > Advanced
On the Network mini-tab, check the box for "Override automatic cache management" to limit the space that Firefox uses.
Or, if your AV software allows you to exclude folders in a scheduled or manual scan, you could exclude the folder. Not sure you really want to do that, though, because sometimes a cached file won't be recognized as malware when you first encounter it, only days later, and it would be nice to clear out undesirable files.