I accidentally gave my USB to my friend and then I realized it had some important files of mine. Is there any way I can know if he got something from the USB?

  • 110
    If he's a friend can you go analog and just ask him?
    – HashHazard
    Commented Oct 10, 2018 at 17:35
  • 6
    @HashHazard for sure he will deny Commented Oct 10, 2018 at 19:59
  • 17
    @HarrySattar unless he doesn't deny it. If he says "yes" then you know.
    – schroeder
    Commented Oct 10, 2018 at 20:57
  • 63
    @HarrySattar Just remember it's fairly toxic to assume your friends will lie to your face. This is on you. If your friend had done absolutely nothing wrong, you're already assuming he had copied your files and will lie about it, which is, based on current information, a situation you completely made up.
    – Nelson
    Commented Oct 11, 2018 at 1:20
  • 3
    @Nelson Actually in those files I had my final project. Which he was struggling to create. And I know him he will take advantage of that mistake.Still should I ask him? Commented Oct 11, 2018 at 5:25

5 Answers 5


No logs are recorded on the USB itself around file accesses. At best, you might know if the files were changed by looking at the file timestamps, which can sometimes happen just by opening them, depending on the program opening them.

But there will be no way to determine, by looking at the USB, if the files were copied.

  • 3
    There will be timestamps in the metadata of the files (right click and choose "Properties" or choose the "Details" view in File Explorer). Those other file activities you ask about are not recorded in Windows file systems.
    – schroeder
    Commented Oct 10, 2018 at 17:03
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    This assumes that your friend didn’t reset the access time stamp afterwards which is trivial if you care about it. Commented Oct 10, 2018 at 20:27
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    @DavidFoerster hence the "at best". And even I had to look it up since you mentioned it, so I'm not sure that "trivial" can equate to "likely".
    – schroeder
    Commented Oct 10, 2018 at 20:32
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    @DavidFoerster assuming, more importantly, that the friend didn't have the foresight of mounting the drive read-only. Commented Oct 10, 2018 at 21:00
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    I'd suggest adding to this answer: do not attempt to view access timestamps using Explorer. Just opening the folder containing the files with Explorer can cause it to read the files in order to produce a preview image, thus losing the access time information. Use a command prompt and dir /ta to get the information. But as pointed out by TobySpeight below, FAT filesystems (which is almost certainly what's on the device) don't track update times anyway, so the information almost certainly doesn't exist.
    – Jules
    Commented Oct 11, 2018 at 13:44

There is no way to be sure by strictly technical means.

On the one hand, if your friend has antivirus software installed, it would probably scan your USB stick as soon as it was plugged in their machine; and this would be completely indistinguishable from data being read as a part of copy operation.

On another hand, if they would like to cover their tracks, there are many ways to reset the timestamps, and to prevent their change in the first place.

So... ask them? Get access to their machine and check for the copies your files (if they agree)? Tell them that your data was sensitive and kindly ask to delete it if they accidentally copied it? These might be the questions for Interpersonal and Law SE's; security-wise, your data are already compromised.


It depends on what kind of filesystem is on the disk. Most filesystems retain an access time that can be viewed with ls -lu, provided the "friend" mounted the filesystem read/write. (Note: apparently Windows OSes have no equivalent to ls -lu, so this won't be useful if that's what you have).

If the "friend" mounted the filesystem read-only (or with noatime or similar options), or the disk has a filesystem that doesn't store access times (notably FAT and derivatives), or he covered his tracks by using utime() after reading, then you won't see this evidence.

Alternatively, you might get a "false positive" if something on his system read the file autonomously (e.g. for generating summaries, or looking for malware), but he didn't see the contents or copy the files.

In the end, what little information that is recorded on the media tells you very little about whether the information was accessed, and if so, how it was accessed.

  • If you know what the Windows equivalent of ls -lu is, then please edit it in. As I know nothing about Windows, I'm not qualified to do so. I'm not even sure that Windows can actually mount any filesystems other than its native ones (and possibly ISO 9660? But that doesn't record access times either, for obvious reasons). Commented Oct 11, 2018 at 9:10
  • 4
    The Windows equivalent of ls -lu is dir /ta, although it is somewhat less likely to be useful due to the prepensity of various Windows software (including Explorer) to automatically open and scan any files of types that it recognizes in order to show previews, along with the fact that many users install "tweak" software that often recommends disabling access time updates for performance reasons. Also, as Windows by default formats removable storage devices as FAT, the information is not likely to be present in any case, unless OP intentionally formatted the device as NTFS.
    – Jules
    Commented Oct 11, 2018 at 13:40
  • 2
    TBH, it really hadn't occurred to me that it might have been in a Windows environment when I read the question. If it had even suggested that, I wouldn't have bothered answering. Commented Oct 11, 2018 at 14:04
  • Also I am probably not the only one, who have in fstab set noatime for all media (for elimination of writing timestamps repeatedly, when I do not use prorams, that rely on them - mutt and like)
    – gilhad
    Commented Oct 13, 2018 at 6:48

You could try dir /T:A and compare with dir /T:C

/T TimeField    Specify the time field displayed 
and used for sorting. TimeField may be any of the
following letters.

  C : Creation time.
  A : Last access time.
  W : Last write time.

For instance, when you use the option "/T:C," the 
time listed is when the file was created.

Refer: https://www.computerhope.com/dirhlp.htm


By default, there will be no record of such activity.

When a file is accessed or changed, either the OS or the application can update its "last write" or "last access" property.

Per Microsoft's documentation:

NTFS also permits last access time updates to be disabled. Last access time is not updated on NTFS volumes by default.

Your friend could copy any file(s), and I would not expect the "last access" date to change.

In addition, any auditing for failed/successful attempts to access files would be recorded in the Security log on his computer.

An Inconclusive Method

The only other method is checking for foreign SIDs on file/folder ACLs. If you look at the permissions on a file (on the Security tab), unresolved SIDs may appear.

Unresolved SIDs appear as long strings, such as S-1-5-21-3624371015-3360199248-30038020-3220, rather than human-readable names like SYSTEM, Network Service, or JohnSmith.

Note that foreign SIDs will only be added if he took ownership of files or modified permissions, so the absence of such SIDs does not indicate a lack of access.

  • This is the correct answer. Even if the pendrive uses NTFS (unlikely), last access times are not updated by default since Vista.
    – kinokijuf
    Commented Oct 15, 2018 at 4:47
  • @kinokijuf Right, and even if they were updated, it doesn't mean that the files were copied, it just means they were accessed, for example opened for viewing.
    – ChatterOne
    Commented Oct 15, 2018 at 9:36

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