Tracking down who removed files

By | May 10, 2016

Let’s assume you have a shared folder on a server which is accessible by all employees in your company. The users commonly copy some documents into this folder to let the others to work with these shared documents. One day you discover that some files unexpectedly disappeared from the shared folder. Usually this means that someone deleted these files (consciously or unconsciously). Now we need to detect the person who removed the files.

First, you need to setup Windows security auditing to monitor file access (and optionally logon) events. Of course, you should do it right after creating a shared folder and granting access to it (post factum setup won’t help you) . This article describes how to setup security auditing and audit file access and logon events.

If you correctly setup file access auditing for your shared folder, “File system” events will appear in Security log on every attempt to open file inside the folder.

file system auditing

So be sure that the maximum log size for Security log is set to a reasonable value (or you have a chance to lose old events). Microsoft recommends 4GB for most of Windows, but this depends on different factors – I prefer much smaller sizes with autobackup option.

Event 4660 occurs when someone removes a file or a folder. But its event description doesn’t contain the file name:

An object was deleted.

Subject:
            Security ID:                  S-1-5-21-3946697505-1589476648-2597793080-1114
            Account Name:                 mike
            Account Domain:               FSPRO
            Logon ID:                     0084C195

Object:
            Object Server:   Security
            Handle ID:        00000AC8

Process Information:
            Process ID:       00000004
            Process Name: 
            Transaction ID: {00000000-0000-0000-0000-000000000000}

In fact, when a user deletes file, Windows registers several events: 4663 and then 4660. It can also register event 4656 before 4663).

Here is a sample of 4663 event description:

An attempt was made to access an object.

Subject:
            Security ID:                  S-1-5-21-3946697505-1589476648-2597793080-1114
            Account Name:                 mike
            Account Domain:               FSPRO
            Logon ID:                     0084C195

Object:
            Object Server:   Security
            Object Type:     File
            Object Name:     C:\shared\Data\_DSC9978.JPG
            Handle ID:       00000AC8

Process Information:
            Process ID:      00000004
            Process Name: 

Access Request Information:
            Accesses:        DELETE
            Access Mask:     10000

You can notice that “Access Request Information” group contains Accesses: DELETE and Access Mask: 10000 parameters.

So we can just filter security event log by Event ID = 4663 and Access Request Information\Accesses = DELETE (and if you enabled auditing for several folders, but want to check a specific one, you should also add filter by Object\Object Name):

event 4663 - filter deleted events

Now we can see all “file delete” events with file names.

This method works most of time, but I wouldn’t call it perfect. First, nobody guaranty that Accesses will be DELETE all the time (although you can try Access Request Information\Accesses Contains DELETE). Second, 4663 event occurs on access attempt. In some cases, e.g. if your file is protected, event 4660 won’t appear. So to get more accurate picture, we should rely upon 4663 events and get details from the previous events. Event Log Explorer features Linked Filter, which allows you to link events in security log by description parameter. Look again at 4660 and 4663 event samples. You can link them by Object\Handle ID parameter. Note that Linked Filter scans events from top to bottom, so make sure that you sorted events from new to old (our base event will be 4660).

linked filter - events 4660-4663

Here I got the same result as before.

Now you can just display who deleted files. Event description keeps these details in “subject” group. I will use custom columns to show these details in the list:

custom columns-deleted files

Here is the result of adding custom columns:

showing-users who deleted files

You probably noticed that I added Logon ID along with User name. Using the Logon ID, we can detect from which machine user FSPRO\mike deleted files.

Just set a new filter for event id = 4624 (An account was successfully logged on):

looking for machine - filter by event 4624

And we are getting the machine name and its IP address

workstation name and ip address

 

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