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Updated 9/11 - "Excel cannot open the file [filename] because the file format or file extension is not valid." opening Office files

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There is currently an ongoing situation where users may encounter an error when trying to open Office documents. The error can happen opening any Office file type, not just Excel files. For Excel file types, the error says: "Excel cannot open the file [filename] because the file format or file extension is not valid. Verify that the file has not been corrupted and that the file extension matches the format of the file."

For Microsoft Word, the error may read differently: "The file cannot be opened because there are problems with the contents" or "The file [FileName] cannot be opened because there is a problem with the contents".

We have confirmed that this can also affect PowerPoint files, AutoCAD files and JPEG images.

This problem has been confirmed to be caused by malware on the affected machine. There are now two known variants of malware which causes this problem: Win32/Crilock.A and Win32/Buma!rts.  They have both been identified as a new family of ransomware.

In order to clean your machine, run Microsoft Safety Scanner (https://www.microsoft.com/security/scanner/en-us/default.aspx). If infected, Safety Scanner should clean the virus from the system, however it will not repair corrupted files. You will still need to restore those from a backup. A detailed analysis of affected files submitted to Microsoft for investigation has revealed the files are encrypted with a private and public key. The files cannot be recovered without the private key, which is more than likely held by the attacker. The premise of ransomware is such that if a person pays the ransom the key is provided to "unlock" the files.

Other resources:

Microsoft Word Support Blog: https://blogs.technet.com/b/wordonenotesupport/archive/2013/09/09/quot-cannot-open-the-file-because-the-file-format-or-extension-is-invalid-quot-opening-office-files.aspx

Microsoft PowerPoint Support Blog: https://blogs.technet.com/b/bgp/archive/2013/09/09/3595491.aspx

Comments

  • Anonymous
    April 05, 2016
    Dannt's solution seem to have worked for someone but but for my case i cannot open the file. please advise me on how to start the process i.e how sholud i get to stage one "1. rename the file and remove the .xlsx or .xls extention"
  • Anonymous
    April 05, 2016
    #Dannt, i have tried to remove the extension. Yes, the file changed to white but when i navigate to the file location from start menu through blank excel sheet but the renamed file is not visible. please advise me on how to proceed.
  • Anonymous
    May 04, 2016
    The comment has been removed
  • Anonymous
    June 26, 2016
    we are facing problem Excel cannot open the file [filename] because the file format or file extension is not valid. verifythat the file has not been corrupted and that the file exention matches the format of the file ...... please help
  • Anonymous
    July 09, 2016
    do you know how to do it in windows 8? i am facing the same issues.thanks for your help.
  • Anonymous
    July 18, 2016
    No puedo trabajar con mi excel siempre al guardarse me indica que tiene error o algún problema y no puedo " guardar como"- la verdad excel en este office 365 me esta dando demasiados problemas al no poder aprovecharlo y utilizarlo100%
  • Anonymous
    August 10, 2016
    I have save all my excel files in usb. now some excel file can not open and it has a message asExcel cannot open the file ‘A.xlsx’ because the file format or file extension is not valid. Verify that the file has not been corrupted and that the file extension matches the format of the file.can you please help me how to open this fileThanks
  • Anonymous
    August 22, 2016
    Hi Dannt,As per your suggestion we have done the steps what you have shared but the file is opened in different language.All the important files are there in that excel sheet.Need your help on this pls.
  • Anonymous
    September 08, 2016
    The comment has been removed
  • Anonymous
    November 10, 2016
    A quicker and a hassle free option would be to change the file extension from .xlsx to .xls which allows you to open the excel file and get access to your data.
  • Anonymous
    December 17, 2016
    no puedo abrir el excel
  • Anonymous
    January 02, 2017
    This problem has been confirmed to be caused by malware on the affected machine. There are now two known variants of malware which causes this problem: Win32/Crilock.A and Win32/Buma!rts. They have both been identified as a new family of ransomware.If you knew the reason for the problem why do you not clean it and if necessary give it a new suiteable codeendingsThe worst case as you do today just take the information away and I have to make up a new handwritten member list and keep some 300 people updated. And the thing is that you hav taken all information away today. My question is if its useful to use a system and keep stupied problems. This problem didn´t exist in W7.