How do I know for sure if ESET got rid of a Trojan Horse?

[Guest Niels]

Hello,

I recently got a Trojan Horse via a USB key I connected to my laptop after it was connected to another computer.

At first I didn't know it was a Trojan Horse. My USB key just had new folders (weird ones: one called usbfiles, another one called Winfiles which was in fact an .exe, and a third one I can't remember the name), and after some research (and some clicks on that Winfiles folder...) I strated to figure out it could have been a virus, so I downloaded ESET Smart Security (which I had not done yet) that indicated me that my computer was infected by a Trojan Horse (hidden in a Windows-like name, stationed - if I do remember well - somewhere in C:/users/me/AppData/Roaming/...). I did a scan with ESET, it proposed me to delete the file (I accepted) and to block another one (I accepted too). But that's all.

So I did other scans, and everytime ESET has no alert for me, but it tells me with orange letters that it can't open all the files. My fear is that the Trojan Horse may be in one of these files.
Could you help me with that, explaining to me why ESET can't access all my files, and eventually if the Trojan Horse can still be hidden somewhere in my files.

I thank you very much for this.

 - Niels

Post scriptum: I'm French, so I do apologise if my English is not perfectly correct or if I appear rude or anything like that. That's not my intention at all. If some sentences are not clear enough, do not hesitate to ask me some clarifications.

[Marcos 5,228]

2 minutes ago, Guest Niels said:

So I did other scans, and everytime ESET has no alert for me, but it tells me with orange letters that it can't open all the files. My fear is that the Trojan Horse may be in one of these files.

Could you help me with that, explaining to me why ESET can't access all my files, and eventually if the Trojan Horse can still be hidden somewhere in my files.

It is normal that some files are being exclusively used by the operating system or you don't have permissions to read them. These are then reported with an error opening the file.

[itman 1,739]

You should also purchase an Eset consumer product of your choice. All Eset products will prompt you upon insertion of removable media to scan the drive for malware which is a necessity when the drive has been used on any external device. 

[Guest Niels]

Hi Marcos,

Thank you for your answer. I understand that it is normal that Eset can't access the files I do not have any access myself. (A extra question here would be: if these are my files, why coulnd't I get any access to them?) But despite this being a normal situation, I am worried that a virus would, because Eset can't access these files, hide into them. Is it something possible?

I thank you very much.

 - Niels

Post scriptum: How long is the list of the files Eset and I can't access? It seems to me that the list reported is very very long.

[Guest Niels]

Hi itman,

Thank you for your answer too.
I usually never insert my removable medias on any other devices than mine. It was such an exception that I forgot I did it.
But I'll consider purchasing an Eset consumer product, since I failed alone.

Thank you a lot.

 - Niels

[Marcos 5,228]

If ESET cannot access some files, then you should not be able to access them either. If you run a scan as an administrator and some files cannot be scanned, then it's highly unlikely that malware could access them.

[Guest Niels]

Marcos,

Thank you very much for your answer. I am now reassured.

Have a nice evening.

Thank you again.

 - Niels