Don’t accept corrupted files

With greater reliance on technology for student work, we run into the possibility that there can be technology issues with student work – connection problems, version issues, lack of access, etc. Though as the technology, and availability thereof, increases, these issues seem to be declining.

But there is one issue that seems to be on the increase, and that is students having problems with files becoming corrupted and inaccessible. As supportive educators, we don’t want to be punitive if there are legitimate issues. But having been around the sun a few times, I know a statistical rat when I smell one.

As computers become faster, storage is ubiquitous, and there is less and less saving to removable media the opportunity for files to become corrupted by accident is declining. It can still happen, if for example a flash drive is removed while a file is being copied or saved, or the computer crashes while a file is being saved, but since saving a file is so fast, the chances of this are very, very slim. So what’s going on?

Mainly, this: There are plenty of sites, and YouTube videos, and how-to’s about corrupting your own files so they can’t be opened. Then it is just a matter of acting surprised, and bingo! The teacher asks you to please re-do the work as quickly as possible, giving you extra time to complete the work.

Well, I’m on to them, and now so are you.

So let’s look at a few ways files can be corrupted, and how to recognize a corrupted file, and how to tell the contents of the file (I am a PC user, not a mac user, so I will focus on what I know, but I’m sure if you are a mac user you can find someone who can help you out similarly).

1. Changing the file type. This one is dead easy, but also very easy to detect. The idea is to take a file – such as an image or a video file, or an exe or whatever you have around, and simply change the extension to .docx or .pptx instead of .jpg or whatever it was. Since most users don’t even have the file extensions visible, this one is fairly effective. The application just chokes, and is unable to “repair” the file. The solution? Open the file with notepad. You can just open notepad and drag and drop the file in. While most of it will look like gobbledygook, there will be clues, mainly in the first line, where you may see something like “PK    »¬fB” or “JFIF” or some other clue. A quick Google search may help you identify the file type – PK is a zip file (or an Office document – since office docs are a collection of information files saved together as a zip), JFIF is a jpg image, and so on. Try changing the file extension and opening in another application. Other clues lie elsewhere in the file – Word documents may end with a sequence like:

“word/numbering.xmlPK-    ! ÷ÝJÆ¿ Q  °Z word/people.xmlPK-    ! ©Ó¢Ùñ ‰  œ\ customXml/item1.xmlPK-    ! —IqE   æ` word/fontTable.xmlPK-    ! õøÍ ¾  [c word/commentsExtended.xmlPK-    ! $ï¶D ÿ  _e word/webSettings.xmlPK-    ! ¶Ëëš\ ˜  ¤f docProps/core.xmlPK   — 7i”

Which clearly identifies it as a word doc. So if you get something purporting to be a “corrupted” word doc, and it has none of these, then it is likely not actually a word doc.

Powerpoints also have clues, like: “ppt/slides/_rels/slide9.xml.rels¬MKÄ0†ï‚ÿ!Ìݤ-“‹lº<Éú†dš›2Y±ÿÞˆ—-“. If there is nothing like this, then it probably isn’t a powerpoint.

2. Corrupting the header. It is easy enough to delete a few characters from the start of a file (using Notepad as above, for example), which will render it completely unusable. However, if you can go into the file in notepad as above, you should be able to see if it is the right type of file. If the internal clues are still there but that first line with the file info is missing, it probably had that info deliberately deleted. Unfortunately, it is almost impossible to recover a file corrupted in this way. But I’m working on it…

3. Online tools. Yes, there are tools online specifically to mess up your files so they data cannot be retrieved. A hallmark of these tools is that they overcorrupt, so the file is comletely unrecognisable. Compare the screenshots below of a powerpoint file and the resulting corrupted file:





Though hard to prove, but there is no way for an office document or powerpoint to wind up looking like that by accident.

So, with this information,  what do we do?

Firstly, there are proactive strategies such as having students submit drafts regularly, and requiring students to make backups. Also, you can have students use tools such as Google Drive – where the back end file is inaccessible and all changes are tracked –  in order to minimize the risk of file corruption (intentional or otherwise).

Secondly, arm yourself with knowledge of what tricks people may be up to. If you suspect a file has been tampered with, drop it into notepad and have a look, or bring it (and a copy of this post) to your IT department and have them look at it.

Lastly, and perhaps most importantly, keep the lines of communication open, and let students know that legitimate reasons for a delayed submission are open for discussion, so that maybe they will never feel like they have to resort to this.


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