Attachment Types Blocked By Default

Situation – You have not received emails you were expecting, and they have been blocked by a General EXE block. Which attachments does Spambrella block by default?

Solution – By default, Spambrella blocks executable file types as they can be malicious. This article lists the file types blocked and two ways you can circumvent the block to receive emails that are necessary from a trusted sender by either:

  • Creating a custom filter OR
  • Zip & Password Protect the file

Attachment Types Blocked By Default

NOTE: Spambrella reserves the right to block attachment types not listed below in cases where a threat has been detected

FILE TYPE

FILE EXTENSION

DESCRIPTION

Executable

.exe

"EXE is short for "executable," and it is the standard file extension used by Windows programs"

Dynamic-Link Library

.dll

"A DLL file is a compiled library that contains a set of procedures and/or drivers that are referenced and executed by a Windows program"2

Batch File

.bat

"A BAT file is a DOS batch file used to execute commands with the Windows Command Prompt (cmd.exe)"3

Visual Basic

.vb

"A VB file is a project item file written in the Visual Basic language; an object-oriented programming language created by Microsoft for use with the .NET Framework. It contains Visual Basic instructions in ASCII text format."4

JavaScript

.js

"A JS file is a text file containing JavaScript code that is used to execute JavaScript instructions in web pages. It may include functions that open and close windows, validate form fields, enable rollover images, or create drop-down menus."5

 

How to Bypass

There are two ways to bypass the general block on the attachments listed above:-

  • Implement a custom filter to allow an attachment from a specified sender
  • Have the sender zip & password protect the file before sending

Important: Before bypassing the general block on the above attachments, it is imperative that you verify its authenticity with the original sender.

Custom Filter

  1. Navigate to Security Settings > Email > Filter Policies.
  2. Click New Filter.
  3. Give the filter an appropriate name.
  4. For Type, select Inbound.
  5. Click Continue.
  6. Use the following conditions for your filter:

Bypass-Exe

The above attachment is an example to allow .exe files. This will need to be changed based on the file extension you wish to allow, such as *.dll or *.vb

Zip & Password Protect

Using a file archive like 7zip, the sender can zip and password protect the attachment being blocked before sending. A password-protected file cannot be opened and it’s content scanned. The attached file will be passed in this case as there would be nothing to match against known problem types.