The uploading of files into Moodle courses by Students or Teachers may be restricted by file blocking measures. The reason could be to require the use of particular file formats inside an online course, or to protect VCC from viruses or malicious executables that could be uploaded through Moodle's interface.
File Type restrictions in Moodle Assignments
In Moodle assignment activities, the Instructor can restrict what kinds of files Students can upload for their submissions.
There are good reasons for doing this:
- A format-specific activity: The instructor wants to receive files in a particular file format as part of the goal of the assignment (e.g. only PowerPoint files can be submitted for a PowerPoint authoring course).
- Compatibility issues: The instructor doesn’t want to accept file types which they cannot open on their computer (e.g. a proprietary Apple image format like HEIC may need conversion before opening in Windows).
- Download/upload efficiency: Some file types may be larger in storage size than other more-compressed types (e.g. TIFF vs. JPG, or WAV vs. M4A).
- Legibility or accessibility: A document format may be required for text content. A photograph or image scan of a written page won’t do (e.g. require a Word or PDF format, instead of a JPG or PNG image).
When you specify allowed file types in your assignment, Moodle will show those restrictions to the Student right when they select a file, and prevent the upload of disallowed file types.
A sample File restriction blocker error message in a Moodle activity:
System-wide FileType blocker plugin
System-wide, VCC Moodle also restricts the upload of certain kinds of files for security and storage reasons:
- Video file formats (e.g. MP4, MOV, MPG, etc.)
The size of video recordings can consume storage space very quickly, and this can may over-burden Moodle’s system performance and storage cost. Video files should be uploaded into VCC’s Kaltura media platform.
- Large data file formats (DWF, etc.)
Extremely large data files (e.g. hundreds of megabytes or even gigabytes) can rapidly fill space in Moodle’s database. These should be stored in an external cloud location, like VCC’s Microsoft OneDrive)
- Unknown or Potentially Risky File Types
If a file’s file extension (e.g. .docx, .jpg) doesn’t match the filetype described in the file’s own internal header, the file might be maliciously misrepresenting its content. (For example, bad actors can create files that appear to be graphic images, but which actually contain malicious .exe executables that could infect or corrupt data once opened.)
File Type Blocking Behaviour and Whitelist
In VCC Moodle, file type blocking is managed using a custom software plugin called "Mime Blocker Antivirus", that analyzes a file's file header and compares it to a “whitelist” of accepted file types. If a file type is unknown to us or to the authors of our file blocker tool, it will likely not be on the whitelist.
Error Message from Moodle’s file type blocker:
This system-wide behaviour is outside of Instructor and Manager control in Moodle.
Here's what you can do, and how eLSupport can help you:
Work-arounds you can try:
- Put your file inside a Zip archive. We've let our file type blocker allow Zip files.
- If the file was created by a proprietary or specialty third-party application (for example, a vendor tool that exports to MS Word format), try re-saving the document using its native application
- Try re-saving the file to a different version of its file format (e.g. .doc instead of .docx).
File Format Allowances by eLSupport
Upon request, eLSupport might be able to add your special file format to our blocker’s “whitelist”, so that it won’t be blocked in the future.
With so many different software applications in use at VCC, allowing a new file format is often a process of discovery and analysis. eLSupport may request a sample file, and analyze its header to see if it matches the file’s extension. eLSupport also searches for examples of the file’s use and to learn about the applications and vendors that create or use that file type.
Examples of files being blocked:
- Office documents with password-protection: The file may have a ".docx" file extension, but will have the file header “application/encrypted” because of the password protection.
- File types that have been found to contain malicious content: "application/octet-stream" and “application/encrypted”
- File types unknown to eLSupport: If your software application uses a unique or obscure file format that we weren’t aware was being blocked, send us a sample file and we can inspect it as described above.
Related Resources: