Keyloggers

I am a user of Nod32 version 4 and have enabled the checkbox for potentially unsafe applications and have a keylogger installed on my system. I have run a scan of my entire system and nothing was detected during the scan.

My question is why does Nod32 not find this keylogger ?

Could it be because its hidden so well on the file system that it does not get scanned ?

Could it also be that it does get scanned but its byte code does not display malicious activity ?
Could it be also be that it goes get scanned but there is no history/signature of the file that it evades detection as a threat ?

I would really like to know how could it be saved on the file system either as a hidden file or as an alternative data stream or using another advance method.

Comments could be appreciated and thanks in advance

 

I'd suggest submitting the file to ESET per the instructions here.