Converting Attached Documents in Emails to Text Files

Many email-borne viruses are delivered through innocent-looking attachments. Imagine someone in your accounting department getting an Excel Spreadsheet disguised as an invoice. Opening an Excel file originating from an untrusted source can potentially be very dangerous. Risks associated with opening an untrusted document are mitigated if you could somehow convert that Excel sheet into a plain text file. Plain text files cannot have scripts, embedded objects, hyperlinks to foreign sites, or any other feature that can be harmful, which makes them very safe.

Starting from version 8.5, Xeams can convert embedded attachments in an incoming email to their textual representation. Consider the following example:

  • John Doe (john.doe@gmail.com) sends an email with Invoice.xlsx file to your accounting department.
  • There are no signs this message is junk - in other words:
    • It came from a legitimate source (gmail.com)
    • The file is not picked up by anti-virus
    • The content of the email appears good.
  • When this feature is enabled, the recipient will see Invoice.xlsx along with a Invoice.xlsx.txt file in their email.
  • Since opening the text file is safe, the recipient can safely open the file to see if it contains valid data.

Supported Files

The following types of files are supported.

  • Microsoft Word (*.doc, *.docx, *.dot, *.dotx)
  • Microsoft Excel (*.xls, *.xlsx, *.xlt, *.xltx)
  • Microsoft Powerpoint (*.ppt, *.pptx)
  • Microsoft Publisher (*.pub)
  • Adobe Acrobat (*.pdf)
  • Rich Text Format (*.rtf)
  • HTML Files (*.htm, *.html)
  • Compressed Files (*.zip, *.tar, *.jar, *.gz, *.7z, *.ar, *.arj)
  • winmail.dat (MS Outlook Email Format)

Important

This feature does not work in SMTP Proxy server. It is strongly recommended you switch from Proxy to Regular. SMTP Proxy server is no longer considered secure and will be disabled in future releases.

Steps To Enable

  • Click Filter Management/Attachment Conversions
  • Check Enabled box to enable this feature
  • If Include ReadMe.txt is checked, an additional text file ReadMe.txt will be added letting the recipient know about the conversion.
  • Score Threshold, which is set to -400 by default signifies the minimum score. Attachments in emails scoring lower than this value will not be converted.

Rules

  • Conversions only occur for incoming emails. Internal and outbound emails are not modified.
  • Size of the email is less than Maximum actionable size specified under Filter Management/Message Size.
  • Final score of the email is higher than Score Threshold.

Customizing ReadMe.txt

You can modify the contents of ReadMe.txt using the following steps:

  • Using Windows File Explorer (or SSH on Linux), go to $INSTALL_DIR\config, where $INSTALL_DIR refers to the installation folder where Xeams is installed.
  • Look for TextExtractionReadme_XXX.txt, XXX refers to an integer representing a profile number.
  • Modify these files as you like. It contains a variable that is written as ##CONVERTED_FILES##. Leave this text as-is, which serves as a holder for file names at runtime.