Can there be a Trojan inside your system even if the anti-malware don´t detects any?

[HuskyJ]

[strike]Sorry long title.[/strike]

Story

Recently I found a password stealer while doing a PC cleaning. It was the strangest kind of malware as it was stuck to an file that would never be executed at all. So my system technically had a malware but it wasn´t doing anything. Not that it mattered much since I haven´t used this pc for months since I download said file. Since then however I have had this feeling of paranoia of my system actually being infected and I just don´t notice. I ran a malware scan almost twice daily for a week and even now it says that nothing was found. Is it completely safe?

Info

I use malware bytes as my anti-malware. I run a threat scan and a custom check all computer scan whenever I can and nothing as been detected for a month.

The file in question came with a torrent file. I´ll leave the details out, just now it was a file that would´ve never been executed.

 

[USAFRet]

Can there be? Yes. No AV or malware application is 'perfect'.
What else did that torrent (and others) bring into your system?

 

[HuskyJ]

Can there be? Yes. No AV or malware application is 'perfect'.
What else did that torrent (and others) bring into your system?

You mean malware? Nothing. That's what I find so sketchy. The trojan was attached to one, and only one file, and on top of that it was a non executable file so it would never trigger an infection. I have downloaded other torrent files from the same source about 5 times, let alone all other files I've downloaded via torrent, and this was the only warning I've ever gotten. I guess it could've been a fake positive but you can never be sure when it comes to malware.

 

[rgd1101]

there are many attack vector other then executable. like image, movie, pdf, dll, etc. what type of file was it?

 

[HuskyJ]

there are many attack vector other then executable. like image, movie, pdf, dll, etc. what type of file was it?

I believe it was a dll file. The anti-malware said it quarentined and deleted it. This happened a month ago and I've already deleted all related files.