FTMG decompression of GZIP files locally


  • I am experiencing a problem with our FTMG where content that exists on the web in a GZIP format is arriving on my desktop decompressed instead of compressed.  Note that the content  still has the filename with the extention of .gz so from Windows perspective it still thinks the content is compressed.

    I've verified that this is happening on multiple computers that utilze the FTMG and that this behavior is NOT happening when I use a computer that is not attached to the FTMG.

    I cannot find any settings or configuration information that would allow me to turn this "feature" off.

    This only happens for HTTP traffic and does not happen for FTP traffic since I can routinely download other gzip compressed files using the FTP protocol and those files arrive on my local desktop still compressed.

    This is a problem since the software that I'm using - provided by an external agent - is expecting the files that it is working with to arrive fully compressed. This software crashes (as it should) when trying to decompress a file that is already decompressed.

    I have verified that this is happening irrespective of the use of caching, i.e. it happens with the cache turned on and with the cache turned off.

    Note that this problem started about two days ago since the software I have been using for years started crashing two days ago.

    Please provide some advice on how to stop this behavior.

    Sincere yours

    Jerry W. Manweiler, Ph.D.

    Jerry W. Manweiler, Ph.D.

    Friday, October 12, 2012 6:38 PM

All replies

  • Hi,

    It is possible to configure HTTP compression:

    regards Marc Grote aka Jens Baier - - -

    Friday, October 12, 2012 8:03 PM
  • Marc

    Thank you for your reply but I think you are misunderstanding my problem.

    I don't think this is an issue of HTTP compression since as I read that information it implies compression of the http data stream between the forefront server and the outside source.

    What I'm experiencing is that our Forefront server is grapping already gzipped files from a server using the HTTP protocol and is NOT leaving the gzipped file compressed on my local desktop but instead it is decompressing the file on my desktop although it is NOT changing the filename, i.e. still leaves the .gz extension, so that when local (on my desktop) software reads the file it tries to decompress the file and an exception is thrown and causes the software to crash.  I have talked with the author of the software and they will look at trapping the exception but the real issue is that the originally compressed file is being delivered to my desktop uncompressed which it shouldn't.

    I very much need help solving this issue since I have confirmed that it is happening at our Forefront TMG server and not at the local machines.


    Jerry W. Manweiler, Ph.D.

    Tuesday, October 16, 2012 7:08 PM
  • Hi Jerry,

    Were you able to find a resolution for this? I am experiencing the same issue.


    Friday, March 7, 2014 11:29 PM
  • Tim

    I have never been able to figure this out. We actually had to rewrite some of our code that gets compressed files from the internet and works with them because of this issue.  If you figure it out please let me know so that I can fix it here.  I do have to admit that I don't expect an answer from Microsoft since they are no longer supporting FTMG.  I am currently looking at Sophos appliances as a possible replacement system since in the near future we will stop getting antivirus/antimalware updates if I understand correctly but I am expecting to use the FTMG until the end of the year and put the firewall/appliance replacement into server in Q1 or Q2 of 2015.

    Jerry W. Manweiler, Ph.D.

    Friday, April 4, 2014 9:55 PM
  • I found that if you request the files over https they are delivered to the client compressed where http will result in them being decompressed and the gzip encoding header removed.
    Friday, June 8, 2018 10:06 PM
  • Mindbender, thank you for the reply but since Microsoft in their infinite wisdom no longer supports FTMG I switched to using a Sophos appliance about 3 years ago.  It is working great and I am very happy with it.

    Jerry W. Manweiler, Ph.D.

    Friday, June 8, 2018 11:00 PM