Syncplify.me Server! v4.0.34 released

We have just released version 4.0.34 of our Syncplify.me Server! software. This version features the following improvements:

  • Fixed: white-list rejection handling in the FTP(E/S) protocol handler (SFTP was not affected)
  • Improved: license persistence in complex virtual environment featuring partially dynamic virtual hardware (Warning: upgrading to 4.0.34 from any previous version will invalidate your license, so please if you are a customer – before you upgrade – contact us to request a license reset)

Note: if after the update you notice any unexpected behavior in the web interface, just hit Ctrl-F5 in your browser; that will force the browser to reload the page as well as all back-end scripts and update the ones that may have been cached from previous versions of the software.

As usual you can download this new release from our website.

How to prevent uploads of EXE files

Syncplify.me Server! version: 4.0.0+

Some SFTP servers feature a simple “extension exclusion list” so that administrators can specify certain file extensions that the server should not let users upload. But that’s a pretty weak defense, as a clever attacker could always upload an EXE with a fake extension and then rename it or otherwise find alternative ways to run it on the server, thus compromising its security.

Syncplify.me Server!’s scriptable nature, though, allows you to do a lot more than just disallow certain file extensions. Here’s a sample script that can be attached to the “AfterFileUpload” event handler, to identify EXE files that have been uploaded with fake extensions and delete them right away.

The above script is provided as a mere example to identify Windows EXE files. But it could be easily modified in order to identify other file types.

All Windows EXEs, in fact have stable distinguishing features in their binary code, and more precisely: the first 2 bytes (in hex) will always be 4D5A, and the 4 bytes at offset 256 (0x100) will always be 50450000. So if a file has those byte sequences in those exact locations, it’s safe to say it’s a Windows EXE.

Do you need to identify ZIP files instead? The first 4 bytes are always 04034B50.

And so on… many file types can be identified by specific “signatures” in their binary code, that one can easily read using Syncplify.me Server!’s powerful scripting capabilities.