The VFS

Once we selected a client, we often want to quickly look at the client’s filesystem. The Velociraptor GUI has a Virtual Filesystem View (VFS) screen.

The VFS is simply a server side cache of the files on the endpoint. It is merely a familiar GUI to allow to interactively fetch and inspect of the client’s filesystem.

The Virtual Filesystem
The Virtual Filesystem

The VFS consists of a tree view in the left pane and a file listing in the top right pane. The tree view allows us to navigate through the filesystem, starting at the top level. Remember that the GUI is simply viewing data that was previously collected from the client. When clicking on a directory in the tree view that has not been synced from the client yet, the top right pane shows the message No data available. Refresh directory from client by clicking above..

Clicking on the refresh directory button will initiate a directory listing operation on the client, and providing the client is currently connected, will refresh the VFS view. Similarly the recursive refresh directory button will recursively refresh the directory listing from the current directory down.

Clicking on any of the files in the directory listing, will show their properties in the bottom right pane. In particular, listing the directory only populates file metadata, such as timestamps - it does not fetch the file data. In the Stats tab (bottom right pane) we can initiate a download operation from the endpoint by clicking the “Download from client” button .

If you need to download a lot of files, it might be easier to hide the Stats pane (bottom right pane) by clicking the Stats Toggle button and initiating the download by right clicking the Download cell next to the file in the listing.

Once a file is fetched from the endpoint it is stored on the server and we may view it in the VFS GUI. The file is also marked by a floppy disk icon . You can download the collected file from the server by clicking the download icon .

Exporting VFS files

While it is possible to download collected files from the VFS Stats tab this is inefficient for many files. Instead you can click the Prepare Download button to prepare an export Zip file of various files from the VFS.

Exporting files from the VFS
Exporting files from the VFS

This will begin a server side collection that packages the downloaded files specified into a new collection which may then be exported.

Recursively operating on files

Previously we saw how we can list one directory or fetch one file from the endpoint. In many cases it would be convenient to fetch or download entire directories from the endpoint. Clicking on the recursively sync directory button begins a recursive directory listing.

Recursive listing a remote directory
Recursive listing a remote directory

Syncing large directories and downloading many files from the endpoint can take a long time and transfer large amount of data. By default resource limits are enforced that limit the operation to 10 minutes and transferring 1Gb of data. If you accidentally initiated a download of a very large directory you can click the button again to cancel the operation.

Previewing a file after download.

Once a file is fetched from the endpoint it is stored on the server. You can quickly preview the file in the GUI by clicking on the preview button (initially the preview button shows the first few characters from the file, which helps to quickly eyeball the file type).

Previewing files
Previewing files

The Preview screen is a hex viewer with some useful features:

Previewing files
Previewing files

  • Text View: View a text only version of the data (this removes non printable characters from the binary data and shows only ASCII strings).
  • Goto Offset: allows to skip to arbitrary offsets in the file
  • Search file: allows to search the file using Regex, String or Hex String modes.

VFS accessors

The top level directory in the VFS tree view represents the accessor. An accessor is simply a dedicated code used to fetch filesystem information from the endpoint.

The file accessor simply uses the OS’s APIs to list files or directories and fetch data. The ntfs accessor uses Velociraptor’s built in NTFS parser to be able to access hidden NTFS files and Alternate Data Streams (ADS).

Similarly the registry accessor provides file like access to the registry.

Registry Accessor
Registry Accessor

Interactively investigating an endpoint

Although the VFS presents a familiar interface, it is not ideal for quickly finding the files and registry keys we are usually interested in. One would need to know exactly which files are of interest and then click over multiple directories searching for these files.

To automate collection it is better to write special purpose VQL Artifacts to identity the information of interest.

Our next section explores what artifacts are and how we collect them using Velociraptor.